Method and terminal for feeding back channel state information

ABSTRACT

A method and terminal for feeding back channel state information are applied to a 4-antenna system. The method includes: a terminal acquiring channel state information, the terminal performing joint encoding on PMI1 information and RI information into a 4-bit or 5-bit feedback report, or, performing joint encoding on PMI1 information and PMI2 information into a 4-bit feedback report, or, the PMI2 information using 2-bit feedback; and the terminal feeding back the feedback report in a physical uplink control channel.

TECHNICAL FIELD

The present invention relates to the field of communications, and inparticular, to a method and terminal for feeding back channel stateinformation.

BACKGROUND OF THE RELATED ART

In a wireless communication system, a transmitting terminal and areceiving terminal acquire a higher rate by means of spatialmultiplexing and using multiple antennas. Compared with a common spatialmultiplexing method, an enhanced technology is that the receivingterminal feeds back channel information to the transmitting terminal,and the transmitting terminal uses some transmission precodingtechnologies according to the acquired channel information, whichlargely enhances the transmission performance. In single-userMulti-input Multi-output (MIMO), the channel characteristic vectorinformation is directly used for precoding; and in multi-user MIMO,relatively accurate channel information is needed.

In a Long Term Evolution (LTE) plan, the channel information isprimarily fed back using a relatively simple single-codebook feedbackmethod, while the performance of the transmission precoding technologyfor MIMO is more dependent on the accuracy of the codebook feedbacktherein.

The basic principle of the channel information quantization feedbackbased on a codebook will be set forth briefly as follows.

It is assumed that the limited feedback channel capacity is B bps/Hz,and then the number of available codewords is N=2^(B). Afterquantization, the characteristic vector space of the channel matrixforms a codebook space

={F₁, F₂ . . . F_(N)}. The transmitting terminal and the receivingterminal jointly store or generate the codebook in real time (the samefor the receiving terminal and the transmitting terminal). According tothe channel matrix H obtained by the receiving terminal, the receivingterminal selects a codeword {circumflex over (F)} which best matches thechannel from

according to a certain criterion, and feeds back a serial number i ofthe codeword to the transmitting terminal. The serial number of thecodeword is referred to as a Precoding Matrix Indicator (PMI) here. Thetransmitting terminal finds a corresponding precoding codeword{circumflex over (F)} according to the serial number i, so as to obtainthe channel information, wherein {circumflex over (F)} representscharacteristic vector information of the channel.

Generally,

may be divided into multiple codebooks corresponding to Ranks, and eachRank correspond to multiple codewords, to quantize the precoding matrixformed by the channel characteristic vectors under the Rank. In general,there will be N columns in a codeword when Rank is N. Therefore, thecodebook

may be divided into multiple sub-codebooks according to different Ranks,as shown in table 1.

TABLE 1

Number of layers υ (Rank) 1 2 . . . N

. . .

the set of codeword the set of codeword the set of codeword vectors whenthe matrixes when the matrixes when the number of columns number ofcolumns number of columns is 1 is 2 is N

Wherein, when Rank>1, the codewords required to be stored are in a formof matrix, wherein such codebook quantization feedback method is usedfor the codebook in the LTE protocol. The codebook for 4 transmissionantennas in the downlink for the LTE is shown in table 2. In practice,in the LTE, the precoding codebook has the same meaning as the channelinformation quantization codebook. In the following, for the purpose ofuniformity, the vector may also be considered as a matrix with adimension of 1.

TABLE 2 Codeword Total number of layers υ (RI) index u_(n) 1 2 3 4 0 u₀= [1 −1 −1 −1]^(T) W₀ ^({1}) W₀ ^({14})/ {square root over (2)} W₀^({124})/{square root over (3)} W₀ ^({1234})/2 1 u₁ = [1 −j 1 j]^(T) W₁^({1}) W₁ ^({12})/{square root over (2)} W₁ ^({123})/{square root over(3)} W₁ ^({1234})/2 2 u₂ = [1 1 −1 1]^(T) W₂ ^({1}) W₂ ^({12})/{squareroot over (2)} W₂ ^({123})/{square root over (3)} W₂ ^({3214})/2 3 u₃ =[1 j 1 −j ]^(T) W₃ ^({1}) W₃ ^({12})/{square root over (2)} W₃^({123})/{square root over (3)} W₃ ^({3214})/2 4 u₄ = [1 (−1 −j)/{square root over (2)} −j (1 − j)/{square root over (2)}]^(T) W₄^({1}) W₄ ^({14})/{square root over (2)} W₄ ^({124})/{square root over(3)} W₄ ^({1234})/2 5 u₅ = [1 (1 − j)/{square root over (2)} j (−1 −j)/{square root over (2)}]^(T) W₅ ^({1}) W₅ ^({14})/{square root over(2)} W₅ ^({124})/{square root over (3)} W₅ ^({1234})/2 6 u₆ = [1 (1 +j)/{square root over (2)} −j (−1 + j)/{square root over (2)}]^(T) W₆^({1}) W₆ ^({13})/{square root over (2)} W₆ ^({134})/{square root over(3)} W₆ ^({1324})/2 7 u₇ = [1 (−1 + j)/{square root over (2)} j (1 +j)/{square root over (2)}]^(T) W₇ ^({1}) W₇ ^({13})/{square root over(2)} W₇ ^({134})/{square root over (3)} W₇ ^({1324})/2 8 u₈ = [1 −1 11]^(T) W₈ ^({1}) W₈ ^({12})/{square root over (2)} W₈ ^({124})/{squareroot over (3)} W₈ ^({1234})/2 9 u₉ = [1 −j −1 −j]^(T) W₉ ^({1}) W₉^({14})/{square root over (2)} W₉ ^({134})/{square root over (3)} W₉^({1234})/2 10 u₁₀ = [1 1 1 −1]^(T) W₁₀ ^({1}) W₁₀ ^({13})/{square rootover (2)} W₁₀ ^({123})/{square root over (3)} W₁₀ ^({1324})/2 11 u₁₁ =[1 j −1 j]^(T) W₁₁ ^({1}) W₁₁ ^({13})/{square root over (2)} W₁₁^({134})/{square root over (3)} W₁₁ ^({1324})/2 12 u₁₂ = [1 −1 −1 1]^(T)W₁₂ ^({1}) W₁₂ ^({12})/{square root over (2)} W₁₂ ^({123})/{square rootover (3)} W₁₂ ^({1234})/2 13 u₁₃ = [1 −1 1 −1]^(T) W₁₃ ^({1}) W₁₃^({13})/{square root over (2)} W₁₃ ^({123})/{square root over (3)} W₁₃^({1324})/2 14 u₁₄ = [1 1 −1 −1]^(T) W₁₄ ^({1}) W₁₄ ^({13})/{square rootover (2)} W₁₄ ^({123})/{square root over (3)} W₁₄ ^({3214})/2 15 u₁₅ =[1 1 1 1]^(T) W₁₅ ^({1}) W₁₅ ^({12})/ {square root over (2)} W₁₅^({123})/{square root over (3)} W₁₅ ^({1234})/2

Wherein, W_(n)=I−2u_(n)u_(n) ^(H)/u_(n) ^(H)u_(n) in which I is a unitmatrix, and W_(k) ^((j)) represents a vector in the j^(th) column of thematrix W_(k). W_(k). W_(k) ^((j) ¹ ^(, j) ² ^(, . . . j) ^(n) ⁾represents a matrix formed by j₁, j₂, . . . , j_(n) columns of thematrix W_(k).

The principle of the codebook feedback technology in the LTE isintroduced above. In applications, some more specific feedback methodswill be further referred. Firstly, a feedback granularity of the channelinformation will be introduced. In the LTE standard, the minimumfeedback unit of channel information is subband channel information, andone subband is composed of a number of Resource Blocks (RBs). Each RB iscomposed of a number of Resource Elements (REs), and RE is a minimumunit of time frequency resources in the LTE. In the LTE-A, the resourcerepresentation method of the LTE continues to be used. A few Subbandsmay be referred to as Multi-Subband, and many Subbands may be referredto as Wideband. The feedback contents related to the channel informationin the LTE will be described below. The feedback of the channel stateinformation includes Channel Quality Indication (CQI for short)information, PMI and a Rank Indicator (RI for short). The CSI contentswhich are mostly concerned here are PMI information; however, both theRI and the CQI belong to the contents of the feedback of the channelstate information. The CQI is an index for measuring whether the qualityof the downlink channel is good. In the 36-213 protocol, the CQI isrepresented by integer values of 0-15, which represent different CQIlevels respectively, and different CQIs correspond to respectiveModulation and Coding Schemes (MCSs). The RI is used to describe thenumber of available spatial independent channels, which corresponds tothe Rank of the channel response matrix. In the Open-loop spatialmultiplexing and closed-loop spatial multiplexing modes, the UE needs tofeed back the RI information, and in other modes, there is no need tofeed back the RI information. The rank of the channel matrix correspondsto the number of layers.

Some mechanisms related to the channel information feedback in the LTEwill be further described. There are two types of feedback modes foruplink channel information in the LTE, i.e., periodic channelinformation feedback in the Physical Uplink Control Channel (PUCCH) andperiodic/aperiodic channel information feedback in the Physical UplinkShared Channel (PUSCH). The PUCCH is a control channel, which hasrelatively high feedback reliability. However, the feedback resourcesthereof are relatively valuable, and the feedback overhead thereof isstrictly limited. In general, the amount of CSI feedback in one feedbackreport (including one or more of PMI, CQI, and RI) can not exceed 11bits; and if the amount of CSI feedback exceeds 11 bits, it will cause asudden reduction in the performance. The PUSCH may provide relativelymore CSI feedback resources; however, the reliability cannot be ensured,and it will influence the transmission of the data services since theresources for data transmission are to be occupied.

The Long Term Evolution Advanced (LTE-A) system, as an evolved standardof the LTE, supports a larger system bandwidth (up to 100 MHz), and isbackward compatible with LTE related standards. In order to obtainhigher average spectrum efficiency of a cell and improve the coverageand throughput of a cell edge, on the basis of the related LTE system,the LTE-A proposes some feedback enhancement technologies in terms ofcodebook feedback, which primarily enhance the feedback accuracy of thecodebook and compress the overhead using the time correlation and/orfrequency domain correlation of the channel information. The technologycan enhance the spectrum utilization of the International MobileTelecommunications-Advance (IMT-Advance) and relieve the shortage ofspectrum resources. At the same time, in consideration that a moretypical application is dual polarization, the enhancement of thecodebook also takes a full consideration of the features of the dualpolarization channel. The principle idea of the feedback technology ofenhanced codebook increases the overhead of the PMI feedback compared tothe feedback in the LTE, and the channel state information isrepresented jointly by feedback of two PMIs in two implementation waysprimarily.

The dual-PMI feedback is defined, and the idea of the feedback way maybe described as follows.

1) The precoding/feedback structure of one subband is jointly determinedby feedback information of two PMI and corresponding codebooks. 2) Thecodebook is known previously by both the base station and the UE at thesame time. The codewords corresponding to the feedback of the PMI maychange at different times and in different subbands. 3) One PMIindicates the attributes of a wideband or a long-term channel. The otherPMI indicates attributes of a subband or a short-term channel. 4) Onematrix may be a fixed matrix, without feedback. At this time, it isequivalent to degenerate to single-PMI feedback (which may be used incases of high-rank and low-rank uncorrelated channels).

It can be seen that a new structure based on dual-PMI feedback isproposed in terms of channel information feedback. For Rank=r, wherein ris an integer, the difference from the previous 4Tx codebook is thatwhen single-codebook feedback equivalent to the dual-codebook is used,the feedback of the codewords in the corresponding codebook needs thefeedback of two PMIs to represent the information thereof. The singlecodebook equivalent to the dual codebooks may generally be representedas the following table 3.

TABLE 3 i₂ i₁ 0 1 . . . N2 0 W_(i) ₁ ,_(i) ₂ W_(i) ₁ ,_(i) ₂ W_(i) ₁,_(i) ₂ W_(i) ₁ ,_(i) ₂ 1 W_(i) ₁ ,_(i) ₂ W_(i) ₁ ,_(i) ₂ W_(i) ₁ ,_(i)₂ W_(i) ₁ ,_(i) ₂ 2 W_(i) ₁ ,_(i) ₂ W_(i) ₁ ,_(i) ₂ W_(i) ₁ ,_(i) ₂W_(i) ₁ ,_(i) ₂ 3 W_(i) ₁ ,_(i) ₂ W_(i) ₁ ,_(i) ₂ W_(i) ₁ ,_(i) ₂ W_(i)₁ ,_(i) ₂ . . . W_(i) ₁ ,_(i) ₂ W_(i) ₁ ,_(i) ₂ W_(i) ₁ ,_(i) ₂ W_(i) ₁,_(i) ₂ N-1 W_(i) ₁ ,_(i) ₂ W_(i) ₁ ,_(i) ₂ W_(i) ₁ ,_(i) ₂ W_(i) ₁,_(i) ₂ N1 W_(i) ₁ ,_(i) ₂ W_(i) ₁ ,_(i) ₂ W_(i) ₁ ,_(i) ₂ W_(i) ₁ ,_(i)₂

Here, W_(i) ₁ _(,i) ₂ is a codeword jointly indicated by i₁ and i₂, andmay generally be written into a function form W(i₁,i₂), and there isonly a need to determine i₁ and i₂. For example, when r=1, as shown inTable 4, illustrated is a codebook corresponding to LTE-A Rel12 rank1.

TABLE 4 i₂ i₁ 0 1 2 3 4 5 6 7 0-15 W_(i) ₁ _(,0) ⁽¹⁾ W_(i) ₁ _(,1) ⁽¹⁾W_(i) ₁ _(,2) ⁽¹⁾ W_(i) ₁ _(,3) ⁽¹⁾ W_(i) ₁ _(+8,0) ⁽¹⁾ W_(i) ₁ _(+8,1)⁽¹⁾ W_(i) ₁ _(+8,2) ⁽¹⁾ W_(i) ₁ _(+8,3) ⁽¹⁾ i₂ i₁ 8 9 10 11 12 13 14 150-15 W_(i) ₁ _(+16,0) ⁽¹⁾ W_(i) ₁ _(+16,1) ⁽¹⁾ W_(i) ₁ _(+16,2) ⁽¹⁾W_(i) ₁ _(+16,3) ⁽¹⁾ W_(i) ₁ _(+24,0) ⁽¹⁾ W_(i) ₁ _(+24,1) ⁽¹⁾ W_(i) ₁_(+24,2) ⁽¹⁾ W_(i) ₁ _(+24,3) ⁽¹⁾${Wherein},{W_{m,n}^{(1)} = {{{\frac{1}{\sqrt{2}}\begin{bmatrix}v_{m} \\{{e^{j\frac{n\pi}{2}} \cdot e^{j\frac{m\pi}{8}}}v_{m}}\end{bmatrix}}\mspace{14mu} v_{m}} = \begin{bmatrix}1 & e^{j\; 2\pi\;{m/32}}\end{bmatrix}^{T}}}$

When r=2, a candidate codebook Option a, as shown in Table 5-a, is afirst codebook corresponding to LTE-A Rel12 rank2.

TABLE 5-a i₂ i₁ 0 1 2 3 0-15 W_(i) ₁ _(,i) ₁ _(,0) ⁽²⁾ W_(i) ₁ _(,i) ₁_(,1) ⁽²⁾ W_(i) ₁ _(+8,i) ₁ _(+8,0) ⁽²⁾ W_(i) ₁ _(+8,i) ₁ _(+8,1) ⁽²⁾ i₂i₁ 4 5 6 7 0-15 W_(i) ₁ _(+16,i) ₁ _(+16,0) ⁽²⁾ W_(i) ₁ _(+16,i) ₁_(+16,1) ⁽²⁾ W_(i) ₁ _(+24,i) ₁ _(+24,0) ⁽²⁾ W_(i) ₁ _(+24,i) ₁ _(+24,1)⁽²⁾ i₂ i₁ 8 9 10 11 0-15 W_(i) ₁ _(,i) ₁ _(+8,0) ⁽²⁾ W_(i) ₁ _(,i) ₁_(+8,1) ⁽²⁾ W_(i) ₁ _(+8,i) ₁ _(+16,0) ⁽²⁾ W_(i) ₁ _(+8,i) ₁ _(+16,1)⁽²⁾ i₂ i₁ 12 13 14 15 0-15 W_(i) ₁ _(,i) ₁ _(+24,0) ⁽²⁾ W_(i) ₁ _(,i) ₁_(+24,1) ⁽²⁾ W_(i) ₁ _(+8,i) ₁ _(+24,0) ⁽²⁾ W_(i) ₁ _(+8,i) ₁ _(+24,1)⁽²⁾ ${Wherein},{W_{m,m^{\prime},n}^{(2)} = {\frac{1}{2}\begin{bmatrix}v_{m} & v_{m^{\prime}} \\{\varphi_{n}v_{m}} & {{- \varphi_{n}}v_{m^{\prime}}}\end{bmatrix}}},{\phi_{n} = e^{j\;\pi\;{n/2}}},{v_{m} = \begin{bmatrix}1 & e^{j\; 2\pi\;{m/32}}\end{bmatrix}^{T}}$

When r=2, a candidate codebook Option b, as shown in Table 5-b, is asecond codebook corresponding to LTE-A Rel12 rank2.

TABLE 5-b i₂ i₁ 0 1 2 3 0-15 W_(i) ₁ _(+8,i) ₁ _(+8,i+24,i+24,0,0) ⁽²⁾W_(i) ₁ _(+8,i) ₁ _(+8,i+24,i+24,0,2) ⁽²⁾ W_(i) ₁ _(+8,i) ₁_(+8,i+24,i+24,2,0) ⁽²⁾ W_(i) ₁ _(+8,i) ₁ _(+8,i+24,i+24,2,2) ⁽²⁾ i₂ i₁4 5 6 7 0-15 W_(i) ₁ _(,i) ₁ _(,i) ₁ _(,i) ₁ _(,0,2) ⁽²⁾ W_(i) ₁ _(,i) ₁_(,i) ₁ _(,i) ₁ _(,1,3) ⁽²⁾ W_(i) ₁ _(+8,i) ₁ _(+8,i) ₁ _(+8,i) ₁_(+8,0,2) ⁽²⁾ W_(i) ₁ _(+8,i) ₁ _(+8,i) ₁ _(+8,i) ₁ _(+8,1,3) ⁽²⁾ i₂ i₁8 9 10 11 0-15 W_(i) ₁ _(+16,i) ₁ _(+16,i) ₁ _(+16,i) ₁ _(+16,0,2) ⁽²⁾W_(i) ₁ _(+16,i) ₁ _(+16,i) ₁ _(+16,i) ₁ _(+16,1,3) ⁽²⁾ W_(i) ₁ _(+24,i)₁ _(+24,i) ₁ _(+24,i) ₁ _(+24,0,2) ⁽²⁾ W_(i) ₁ _(+24,i) ₁ _(+24,i) ₁_(+24,i) ₁ _(+24,1,3) ⁽²⁾ i₂ i₁ 12 13 14 15 0-15 W_(i) ₁ _(,i) ₁_(+16,i) ₁ _(+16,i) ₁ _(,0,2) ⁽²⁾ W_(i) ₁ _(,i) ₁ _(+8,i) ₁ _(+24,i) ₁_(+24,i1+8,0,2) ⁽²⁾ W_(i) ₁ _(+16,i) ₁ _(,i) ₁ _(,i) ₁ _(+16,0,2) ⁽²⁾W_(i) ₁ _(+24,i) ₁ _(+8,i) ₁ _(+8,i) ₁ _(+24,0,2) ⁽²⁾${Wherein},{W_{m,m^{\prime},m^{''},m^{''\prime},n,n^{\prime}}^{(2)} = {\frac{1}{2}\begin{bmatrix}v_{m} & v_{m^{''}} \\{\varphi_{n}v_{m^{\prime}}} & {\varphi_{n^{\prime}}v_{m^{''\prime}}}\end{bmatrix}}},{\phi_{n} = e^{j\;\pi\;{n/2}}},{\phi_{n^{\prime}} = e^{j\;\pi\;{n^{\prime}/2}}},{v_{m} = \begin{bmatrix}1 & e^{j\; 2\pi\;{m/32}}\end{bmatrix}^{T}}$

When r=3,4, a single codebook feedback technology is used, which usescodebooks of Ranks 3 and 4 in the Rel-8 4Tx. The use of the singlecodebook of Ranks 3 and 4 may be equivalent to considering that i₁=0-15and i₂=0 or i₂=0-15 and i₁=0.

As in the LTE-A, the enhancement of the feedback accuracy makes the sumof overheads required for the feedback of the PMI1 and PMI2 information(which may also be construed as a total feedback overhead correspondingto W) increase relative to the overhead of the single codebook in theLTE, and when the codebook is applied to the feedback of channelinformation in the PUCCH and the PMI1 and PMI2 are transmitted in onesubframe at the same time, the overhead of the CSI feedback of the PUCCHwill exceed the overhead limit of 11 bits, which makes the transmissionperformance of the PUCCH degrade seriously, and seriously influences thesystem. In addition, even if the PMI1 and the PMI2 are transmittedseparately, for example, the PMI1 and the RI are transmitted at the sametime, although the feedback of the PMI+RI does not exceed the overheadlimit of 11 bits, as the increase in overhead will cause an increase inthe bit error rate in a case that the transmission resources are fixed,the bit error rate of the RI cannot be well ensured, and there is thus aproblem that the bit error rate of the RI cannot meet requirements. Whenthe wideband PMI2 and the wideband CQI are transmitted together, anexcessive overhead will results in an increase in the bit error rate,which influences the performance of the system. Finally, when thesubband PMI and the subband index as well as the subband CQI aretransmitted together, the overhead limit of 11 bits will also beexceeded, which seriously reduces the performance. The above problem isan important technical problem to be solved in the related art.

SUMMARY OF THE INVENTION

The embodiments of the present invention provide a method and terminalfor feeding back channel state information, to solve the problem in therelated art that when the channel state information is fed backperiodically, the transmission performance of the system is poor due toa large overhead of the channel state information, and at the same time,to ensure the accuracy of PMI feedback with a limited overhead andobtain better precoding performance.

The embodiments of the present invention provide a method for feedingback channel state information, applied to a 4-antenna system,comprising:

a terminal acquiring channel state information, the channel stateinformation comprising a first class of Precoding Matrix Indicator(PMI1) information and Rank Indicator (RI) information;

the terminal performing joint encoding on the PMI1 information and theRI information into a 4-bit or 5-bit feedback report, wherein thefeedback report is used for indicating one of a set of combinationinformation formed by the RI information and the PMI1 information, andthe set of combination information at least comprises one of:

combination information of RI=1 with M1 PMI1 respectively;

combination information of RI=2 with M2 PMI1 respectively;

combination information of RI=3 with one PMI1;

combination information of RI=4 with one PMI1;

wherein, M1=M2=8, or M1=M2=4, or M1=16 and M2=8, or M1=8 and M2=16, orM1=16 and M2=4, or M1=4 and M2=16, or M1=8 and M2=4, or M1=4 and M2=8;and

the terminal feeding back the feedback report in a physical uplinkcontrol channel.

The above method may further comprise the following features: when M1=8or M2=8, the 8 PMI1 indicate 0^(th), 2^(nd), 4^(th), 6^(th), 8^(th),10^(th), 12^(th) and 14^(th) codewords in the Rel-8 codebookrespectively; wherein the Rel-8 codebook in the present disclosurerefers to the codebook defined in 3GPP TS 36.211 V8.9.0.

The above method may further comprise the following features: when M1=4or M2=4, the 4 PMI1 indicate 0^(th), 4^(th), 8^(th) and 12^(th)codewords in the Rel-8 codebook respectively.

The above method may further comprise the following features: when M1=4or M2=4, the 4 PMI1 indicate 0^(th), 2^(nd), 4^(th) and 6^(th) codewordsin the Rel-8 codebook respectively.

The above method may further comprise the following features: whenM1=M2, the M1 PMI1 are the same as the M2 PM2.

The above method may further comprise the following features: whenM1=M2, the M1 PMI1 are different from the M2 PM2.

The embodiments of the present invention further provide a method forfeeding back channel state information, applied to a 4-antenna system,comprising:

a terminal acquiring channel state information, the channel stateinformation comprising Rank Indicator (RI) information, a second classof Precoding Matrix Indicator (PMI2) information, subband indicationinformation, and channel quality information; and

the terminal feeding back the channel state information in a physicaluplink control channel, wherein, when RI=3 or 4, the PMI2 informationcomprises 2 bits, and the PMI2 indicates one codeword in a first set ofcodewords, and the first set of codewords comprises 4 codewords selectedfrom a codebook corresponding to Ranks 3 and 4 in the Rel-8 codebook.

The above method may further comprise the following features: the firstset of codewords comprises:

using 0^(th), 1^(st), 2^(nd), and 3^(rd) codewords in the codebookcorresponding to Ranks 3 and 4 in the Rel-8 codebook as a first group,using 8^(th), 9^(th), 10^(th), and 11^(th) codewords in the codebookcorresponding to Ranks 3 and 4 in the Rel-8 codebook as a second group,selecting 2 codewords from the first group and putting the 2 codewordsin the first set of codewords, and selecting 2 codewords from the secondgroup and putting the 2 codewords in the first set of codewords.

The above method may further comprise the following features: the firstset of codewords comprises:

using 0^(th), 2^(nd), 8^(th), and 10^(th) codewords in the codebookcorresponding to Ranks 3 and 4 in the Rel-8 codebook as a third group,using 1^(st), 3^(rd), 9^(th), and 11^(th) codewords in the codebookcorresponding to Ranks 3 and 4 in the Rel-8 codebook as a fourth group,selecting 2 codewords from the third group and putting the 2 codewordsin the first set of codewords, and selecting 2 codewords from the fourthgroup and putting the 2 codewords in the first set of codewords.

The above method may further comprise the following features: the firstset of codewords comprises:

using 0^(th), 2^(nd), 3^(rd), and 10^(th) codewords in the codebookcorresponding to Ranks 3 and 4 in the Rel-8 codebook as a fifth group,using 2^(nd), 8^(th), 9^(th), and 11^(th) codewords in the codebookcorresponding to Ranks 3 and 4 in the Rel-8 codebook as a sixth group,selecting 2 codewords from the fifth group and putting the 2 codewordsin the first set of codewords, and selecting 2 codewords from the sixthgroup and putting the 2 codewords in the first set of codewords.

The above method may further comprise the following features: the firstset of codewords comprises:

using 0^(th), 1^(st), 2^(nd), and 9^(th) codewords in the codebookcorresponding to Ranks 3 and 4 in the Rel-8 codebook as a seventh group,using 3^(rd), 10^(th), 8^(th), and 11^(th) codewords in the codebookcorresponding to Ranks 3 and 4 in the Rel-8 codebook as an eighth group,selecting 2 codewords from the seventh group and putting the 2 codewordsin the first set of codewords, and selecting 2 codewords from the eighthgroup and putting the 2 codewords in the first set of codewords.

The above method may further comprise the following features: the firstset of codewords comprises:

8^(th), 9^(th), 10^(th), and 11^(th) codewords in the codebookcorresponding to Ranks 3 and 4 in the Rel-8 codebook.

The above method may further comprise the following features: the firstset of codewords comprises:

12^(th), 13^(th), 14^(th), and 15^(th) codewords in the codebookcorresponding to Ranks 3 and 4 in the Rel-8 codebook.

The above method may further comprise the following features: the firstset of codewords comprises:

0^(th), 2^(nd), 12^(th), and 14^(th) codewords in the codebookcorresponding to Ranks 3 and 4 in the Rel-8 codebook.

The above method may further comprise the following features: the firstset of codewords comprises:

4^(th), 5^(nd), 6^(th), and 7^(th) codewords in the codebookcorresponding to Ranks 3 and 4 in the Rel-8 codebook.

The above method may further comprise the following features: the firstset of codewords comprises:

0^(th), 1^(st), 2^(nd), and 3^(rd) codewords in the codebookcorresponding to Ranks 3 and 4 in the Rel-8 codebook.

The above method may further comprise the following features: the firstset of codewords comprises:

0^(th), 1^(st), 3^(rd) and 10^(th) codewords in the codebookcorresponding to Ranks 3 and 4 in the Rel-8 codebook.

The above method may further comprise the following features: the firstset of codewords comprises:

0^(th), 1^(st), 8^(th), and 11^(th) codewords in the codebookcorresponding to Ranks 3 and 4 in the Rel-8 codebook.

The above method may further comprise the following features: the firstset of codewords comprises:

0^(th), 1^(st), 2^(nd), and 9^(th) codewords in the codebookcorresponding to Ranks 3 and 4 in the Rel-8 codebook.

The above method may further comprise the following features: the firstset of codewords comprises:

1^(st), 3^(rd), 9^(th) and 11^(th) codewords in the codebookcorresponding to Ranks 3 and 4 in the Rel-8 codebook.

The above method may further comprise the following features: the firstset of codewords comprises:

0^(th), 2^(nd), 8^(th) and 10^(th) codewords in the codebookcorresponding to Ranks 3 and 4 in the Rel-8 codebook.

The above method may further comprise the following features: the firstset of codewords comprises:

0^(th), 2^(nd), 3^(rd) and 10^(th) codewords in the codebookcorresponding to Ranks 3 and 4 in the Rel-8 codebook.

The above method may further comprise the following features: the firstset of codewords comprises:

3^(rd), 8^(th), 10^(th) and 11^(th) codewords in the codebookcorresponding to Ranks 3 and 4 in the Rel-8 codebook.

The above method may further comprise the following features: the firstset of codewords comprises:

2^(nd), 9^(th), 8^(th), and 11^(th) codewords in the codebookcorresponding to Ranks 3 and 4 in the Rel-8 codebook.

The above method may further comprise the following features: the firstset of codewords comprises:

2^(nd), 3^(rd), 9^(th), and 10^(th) codewords in the codebookcorresponding to Ranks 3 and 4 in the Rel-8 codebook.

The embodiments of the present invention further provide a method forfeeding back channel state information, applied to a 4-antenna system,comprising:

a terminal acquiring channel state information, the channel stateinformation comprising Rank Indicator (RI) information, a second classof Precoding Matrix Indicator (PMI2) information, subband indicationinformation, and channel quality information; and

the terminal feeding back the channel state information in a physicaluplink control channel, wherein, when RI=1 or 2, the PMI2 informationcomprises 2 bits, and indicates one codeword in a second set ofcodewords, and the second set of codewords comprises:

0^(th), 1^(st), 2^(nd), and 3^(rd) codewords in a codebook correspondingto rank 1 in the Long Term Evolution-Advanced (LTE-A) Rel12 version or afirst or second codebook corresponding to rank 2 in the LTE-A Rel12version; wherein the LTE-A Rel12 version in the present disclosurerefers to 3GPP TS 36.213 V12.0.0; or

0^(th), 1^(st), 8^(th), and 9^(th) codewords in a codebook correspondingto rank 1 in the LTE-A Rel12 version or a first or second codebookcorresponding to rank 2 in the LTE-A Rel12 version; or

0^(th), 4^(th), 8^(th), and 12^(th) codewords in a codebookcorresponding to rank 1 in the LTE-A Rel12 version or a first or secondcodebook corresponding to rank 2 in the LTE-A Rel12 version; or

0^(th), 4^(th), 5^(th), and 12^(th) codewords in a codebookcorresponding to rank 1 in the LTE-A Rel12 version or a first or secondcodebook corresponding to rank 2 in the LTE-A Rel12 version; or

0^(th), 1^(st), 4^(th), and 5^(th) codewords in a codebook correspondingto rank 1 in the LTE-A Rel12 version or a first or second codebookcorresponding to rank 2 in the LTE-A Rel12 version; or

12^(th), 13^(th), 14^(th), and 15^(th) codewords in a codebookcorresponding to rank 1 in the LTE-A Rel12 version or a first or secondcodebook corresponding to rank 2 in the LTE-A Rel12 version.

The embodiments of the present invention further provide a method forfeeding back channel state information, applied to a 4-antenna system,comprising:

a terminal acquiring channel state information, the channel stateinformation comprising Rank Indicator (RI) information, a first class ofPrecoding Matrix Indicator (PMI1) information, and a second class ofPrecoding Matrix Indicator (PMI2) information; and

the terminal performing joint encoding on the PMI1 information and thePMI2 information into a 4-bit feedback report, and

the terminal feeding back the feedback report in a physical uplinkcontrol channel; wherein,

the feedback report is used for indicating one of a set of combinationinformation formed by the PMI1 and the PMI2, and codewords indicated bythe set of combination information comprise codewords in a codebookcorresponding to Rank 1 or a first or second codebook corresponding toRank 2 in the Long Term Evolution-Advanced (LTE-A) Rel12 version.

The above method may further comprise the following features: when RI=1,the codewords indicated by the set of combination information comprisecodewords in the codebook corresponding to Rank 1 in the LTE-A Rel12version, and the codewords indicated by the set of combinationinformation meet:

conforming to a model

${{\begin{bmatrix}u \\{e^{j\frac{m\;\pi}{4}} \cdot e^{j\frac{n\;\pi}{2}} \cdot u}\end{bmatrix}\mspace{14mu} m} = 0},{{1\mspace{14mu} n} = 0},1,2,3,$wherein u is a 2-dimensional column vector.

The above method may further comprise the following features: thecodewords indicated by the set of combination information meet m=0; or

one half of the codewords indicated by the set of combinationinformation meet the model when m=0, and the other half of the codewordsindicated by the set of combination information meet the model when m=1;or

the codewords indicated by the set of combination information meet m=1.

The above method may further comprise the following features: a set ofcodewords indicated by the set of combination information is:

${{\begin{bmatrix}u_{i} \\{e^{{j\theta}_{i}}u_{i}}\end{bmatrix}\mspace{14mu} i} = {0 \sim 15}},$wherein θ_(i) is any real number, and u_(i) is a 2-dimensional columnvector.

The above method may further comprise the following features:

${u_{i} \in \left\{ {\begin{bmatrix}1 \\1\end{bmatrix}\mspace{14mu}\begin{bmatrix}1 \\{- 1}\end{bmatrix}} \right\}},$wherein,in {u_(i), i=0˜15}, 8 values are

$\begin{bmatrix}1 \\1\end{bmatrix},$and 8 values are

$\begin{bmatrix}1 \\{- 1}\end{bmatrix}.$

The above method may further comprise the following features:

${u_{i} \in \left\{ {\begin{bmatrix}1 \\j\end{bmatrix}\mspace{14mu}\begin{bmatrix}1 \\{- j}\end{bmatrix}} \right\}},$wherein, in {u_(i), i=0˜15}, 8 values are

$\begin{bmatrix}1 \\j\end{bmatrix},$and 8 values are

$\begin{bmatrix}1 \\{- j}\end{bmatrix}.$

The above method may further comprise the following features:

${u_{i} \in \left\{ {\begin{bmatrix}1 \\1\end{bmatrix}\mspace{14mu}\begin{bmatrix}1 \\j\end{bmatrix}} \right\}},$wherein, in {u_(i), i=0˜15}, 8 values are

$\begin{bmatrix}1 \\1\end{bmatrix},$and 8 values are

$\begin{bmatrix}1 \\j\end{bmatrix}.$

The above method may further comprise the following features:

${u_{i} \in \left\{ {{{\begin{bmatrix}1 \\1\end{bmatrix}\begin{bmatrix}1 \\{- 1}\end{bmatrix}}\begin{bmatrix}1 \\j\end{bmatrix}}\begin{bmatrix}1 \\{- j}\end{bmatrix}} \right\}},$wherein, in {u_(i), i=0˜15}, 4 values are

$\begin{bmatrix}1 \\1\end{bmatrix},$4 values are

$\begin{bmatrix}1 \\{- 1}\end{bmatrix},$4 values are

$\begin{bmatrix}1 \\j\end{bmatrix},$and 4 values are

$\begin{bmatrix}1 \\{- j}\end{bmatrix}.$

The above method may further comprise the following features:

${u_{i} \in \left\{ {{{{{{{\begin{bmatrix}1 \\1\end{bmatrix}\begin{bmatrix}1 \\e^{j\frac{\pi}{4}}\end{bmatrix}}\begin{bmatrix}1 \\j\end{bmatrix}}\begin{bmatrix}1 \\e^{j\frac{3\pi}{4}}\end{bmatrix}}\begin{bmatrix}1 \\{- 1}\end{bmatrix}}\begin{bmatrix}1 \\e^{j\frac{5\pi}{4}}\end{bmatrix}}\begin{bmatrix}1 \\{- j}\end{bmatrix}}\begin{bmatrix}1 \\e^{j\frac{7\pi}{4}}\end{bmatrix}} \right\}},$wherein in {u_(i), i=0˜15}, 2 values are

$\begin{bmatrix}1 \\1\end{bmatrix},$2 values are

$\begin{bmatrix}1 \\e^{j\frac{\pi}{4}}\end{bmatrix},$2 values are

$\begin{bmatrix}1 \\j\end{bmatrix},$2 values are

$\begin{bmatrix}1 \\e^{j\frac{3\pi}{4}}\end{bmatrix},$2 values are

$\begin{bmatrix}1 \\{- 1}\end{bmatrix},$2 values are

$\begin{bmatrix}1 \\e^{j\frac{5\pi}{4}}\end{bmatrix},$2 values are

$\begin{bmatrix}1 \\{- j}\end{bmatrix},$and 2 values are

$\begin{bmatrix}1 \\e^{j\frac{7\pi}{4}}\end{bmatrix}.$

The above method may further comprise the following features:

${u_{i} \in \left\{ {{{\begin{bmatrix}1 \\1\end{bmatrix}\begin{bmatrix}1 \\{- 1}\end{bmatrix}}\begin{bmatrix}1 \\j\end{bmatrix}}\begin{bmatrix}1 \\{- j}\end{bmatrix}} \right\}},$wherein, in {u_(i), i=0˜15}, when 4 values of u_(i) are

$\begin{bmatrix}1 \\1\end{bmatrix},$m=0, when 4 values of u_(i) are

$\begin{bmatrix}1 \\{- 1}\end{bmatrix},$m=1, when 4 values are

$\begin{bmatrix}1 \\j\end{bmatrix},$m=0, and when 4 values are

$\begin{bmatrix}1 \\{- j}\end{bmatrix},$m=1.

The above method may further comprise the following features:

${u_{i} \in \left\{ {{{{{{{\begin{bmatrix}1 \\1\end{bmatrix}\begin{bmatrix}1 \\e^{j\frac{\pi}{4}}\end{bmatrix}}\begin{bmatrix}1 \\j\end{bmatrix}}\begin{bmatrix}1 \\e^{j\frac{3\pi}{4}}\end{bmatrix}}\begin{bmatrix}1 \\{- 1}\end{bmatrix}}\begin{bmatrix}1 \\e^{j\frac{5\pi}{4}}\end{bmatrix}}\begin{bmatrix}1 \\{- j}\end{bmatrix}}\begin{bmatrix}1 \\e^{j\frac{7\pi}{4}}\end{bmatrix}} \right\}},$wherein, in {u_(i), i=0˜15}, when 2 values of u_(i) are

$\begin{bmatrix}1 \\1\end{bmatrix},$m=0, when 2 values of u_(i) are

$\begin{bmatrix}1 \\e^{j\frac{\pi}{4}}\end{bmatrix},$m=0 when 2 values of u_(i) are

$\begin{bmatrix}1 \\j\end{bmatrix},$m=0, when 2 values of u_(i) are

$\begin{bmatrix}1 \\e^{j\frac{3\pi}{4}}\end{bmatrix},$m=0, when 2 values of u_(i) are

$\begin{bmatrix}1 \\{- 1}\end{bmatrix},$m=1, when 2 values of u_(i) are

$\begin{bmatrix}1 \\e^{j\frac{5\pi}{4}}\end{bmatrix},$m=1, when 2 values of u_(i) are

$\begin{bmatrix}1 \\{- j}\end{bmatrix},$m=1, and when 2 values of u_(i) are

$\begin{bmatrix}1 \\e^{j\frac{7\pi}{4}}\end{bmatrix},$m=1

The above method may further comprise the following features: when RI=2,codewords indicated by the set of combination information comprisecodewords of a first codebook corresponding to Rank2 in the LTE-A Rel12version, and the codewords indicated by the set of combinationinformation comply with a model

${\begin{bmatrix}u_{i_{1}} & u_{i_{2}} \\{e^{j\;\theta_{m}}u_{i_{1}}} & {{- e^{j\;\theta_{m}}}u_{i_{2}}}\end{bmatrix}\mspace{20mu} i_{1}},i_{2},{m = {0 \sim 15}},$wherein θ_(m) is any real number, and u_(i) is a 2-dimensional columnvector.

The above method may further comprise the following features: for all i₁and i₂, i₁=i₂; or in the codewords, one half of the codewords meeti₂=i₁, and the other half of the codewords meet i₂≠i₁.

The above method may further comprise the following features:

$u_{i_{1}},{u_{i_{2}} \in \left\{ {\begin{bmatrix}1 \\1\end{bmatrix}\begin{bmatrix}1 \\{- 1}\end{bmatrix}} \right\}},$wherein, in {u_(i) ₁ ,u_(i) ₂ , i=0˜15}, 8 values of u_(i) ₁ ,u_(i) ₂are

$\begin{bmatrix}1 \\1\end{bmatrix},$and 8 values of u_(i) ₁ ,u_(i) ₂ are

$\begin{bmatrix}1 \\{- 1}\end{bmatrix}_{\;}$respectively.

The above method may further comprise the following features:

$u_{i_{1}},{u_{i_{2}} \in \left\{ {\begin{bmatrix}1 \\j\end{bmatrix}\begin{bmatrix}1 \\{- j}\end{bmatrix}} \right\}},$wherein, in {u_(i) ₁ ,u_(i) ₂ , i=0˜15}, 8 values of u_(i) ₁ ,u_(i) ₂are

$\begin{bmatrix}1 \\j\end{bmatrix},$and 8 values of u_(i) ₁ ,u_(i) ₂ are

$\quad\begin{bmatrix}1 \\{- j}\end{bmatrix}$respectively.

The above method may further comprise the following features:

$u_{i_{1}},{u_{i_{2}} \in \left\{ {\begin{bmatrix}1 \\j\end{bmatrix}\begin{bmatrix}1 \\1\end{bmatrix}} \right\}},$wherein, in {u_(i) ₁ ,u_(i) ₂ , i=0˜15}, 8 values of u_(i) ₁ ,u_(i) ₂are

$\begin{bmatrix}1 \\1\end{bmatrix},$and 8 values of u_(i) ₁ ,u_(i) ₂ are

$\quad\begin{bmatrix}1 \\j\end{bmatrix}$respectively.

The above method may further comprise the following features:

$u_{i_{1}},{u_{i_{2}} \in \left\{ {{{\begin{bmatrix}1 \\1\end{bmatrix}\begin{bmatrix}1 \\{- 1}\end{bmatrix}}\begin{bmatrix}1 \\j\end{bmatrix}}\begin{bmatrix}1 \\{- j}\end{bmatrix}} \right\}},$wherein, in {u_(i) ₁ ,u_(i) ₂ , i=0˜15}, 6 values of u_(i) ₁ are

$\begin{bmatrix}1 \\1\end{bmatrix},$2 values of u_(i) ₁ are

$\begin{bmatrix}1 \\{- 1}\end{bmatrix},$6 values of u_(i) ₁ are

$\quad{\begin{bmatrix}1 \\j\end{bmatrix},}$and 2 values of u_(i) ₁ are

$\begin{bmatrix}1 \\{- j}\end{bmatrix};$and 2 values of u_(i) ₂ are

$\begin{bmatrix}1 \\1\end{bmatrix},$4 values of u_(i) ₂ are

$\begin{bmatrix}1 \\{- 1}\end{bmatrix},$4 values of u_(i) ₂ are

$\begin{bmatrix}1 \\j\end{bmatrix},$and 6 values of u_(i) ₂ are

$\begin{bmatrix}1 \\{- j}\end{bmatrix}.$

The above method may further comprise the following features:

$u_{i_{1}},{u_{i_{2}} \in \left\{ {{{{{{{\begin{bmatrix}1 \\1\end{bmatrix}\begin{bmatrix}1 \\e^{j\frac{\pi}{4}}\end{bmatrix}}\begin{bmatrix}1 \\j\end{bmatrix}}\begin{bmatrix}1 \\e^{j\frac{3\pi}{4}}\end{bmatrix}}\begin{bmatrix}1 \\{- 1}\end{bmatrix}}\begin{bmatrix}1 \\e^{j\frac{5\pi}{4}}\end{bmatrix}}\begin{bmatrix}1 \\{- j}\end{bmatrix}}\begin{bmatrix}1 \\e^{j\frac{7\pi}{4}}\end{bmatrix}} \right\}},$wherein, in {u_(i) ₁ ,u_(i) ₂ , i=0˜15}, 2 values of u_(i) ₁ ,u_(i) ₂are

$\begin{bmatrix}1 \\1\end{bmatrix},$2 values of u_(i) ₁ ,u_(i) ₂ are

$\begin{bmatrix}1 \\e^{j\frac{\pi}{4}}\end{bmatrix},$2 values of u_(i) ₁ ,u_(i) ₂ are

$\begin{bmatrix}1 \\j\end{bmatrix},$2 values of u_(i) ₁ ,u_(i) ₂ are

$\begin{bmatrix}1 \\e^{j\frac{3\pi}{4}}\end{bmatrix},$2 values of u_(i) ₁ ,u_(i) ₂ are

$\;{\begin{bmatrix}1 \\{- 1}\end{bmatrix},}$2 values u_(i) ₁ ,u_(i) ₂ are

$\begin{bmatrix}1 \\e^{j\frac{5\pi}{4}}\end{bmatrix},$2 values of u_(i) ₁ ,u_(i) ₂ are

$\begin{bmatrix}1 \\{- j}\end{bmatrix},$and 2 values of u_(i) ₁ ,u_(i) ₂ are

$\quad\begin{bmatrix}1 \\e^{j\frac{7\pi}{4}}\end{bmatrix}$respectively.

The above method may further comprise the following features: when RI=2,codewords indicated by the set of combination information comprisecodewords of a second codebook corresponding to Rank2 in the LTE-A Rel12version, and the codewords indicated by the set of combinationinformation comply with a model

${\begin{bmatrix}u_{i_{1}} & u_{i_{3}} \\{e^{j\;\theta_{m}}u_{i_{2}}} & {e^{j\;\theta_{n}}u_{i_{4}}}\end{bmatrix}i_{1}},i_{2},i_{3},i_{4},m,{n = {0 \sim 15}},$wherein θ_(m),θ_(n) are any real numbers, and u_(i) is a 2-dimensionalcolumn vector.

The above method may further comprise the following features: the u_(i)₁ ,u_(i) ₂ ,u_(i) ₃ ,u_(i) ₄ meet i₂=i₁=i₄=i₃; or

i₂=i₁ and i₄=i₃, and one half of the codewords indicated by the set ofcombination information meet i₂=i₁=i₄=i₃, and the other half of thecodewords meet i₁≠i₃; or

all codewords indicated by the set of combination information meet i₂=i₁and i₄=i₃, and the number of codewords which meet i₂=i₁=i₄=i₃ is morethan the number of codewords which meet i₁≠i₃; or

one half of codewords indicated by the set of combination informationmeet i₂=i₁=i₄=i₃, a quarter of the codewords meet i₂=i₁, i₄=i₃ andi₁≠i₃, and a quarter of the codewords meet i₁=i₄, i₂=i₃, and i₁≠i₂.

The embodiments of the present invention further provide a terminal,comprising:

a channel state information acquisition unit, configured to acquirechannel state information, the channel state information comprising afirst class of Precoding Matrix Indicator (PMI1) information and RankIndicator (RI) information;

an encoding unit, configured to perform joint encoding on the PMI1information and the RI information into a 4-bit or 5-bit feedbackreport, wherein the feedback report is used for indicating one of a setof combination information formed by the RI information and the PMI1information, and the set of combination information at least comprisesone of:

combination information of RI=1 with M1 PMI1 respectively;

combination information of RI=2 with M2 PMI1 respectively;

combination information of RI=3 with one PMI1;

combination information of RI=4 with one PMI1;

wherein, M1=M2=8, or M1=M2=4, or M1=16 and M2=8, or M1=8 and M2=16, orM1=16 and M2=4, or M1=4 and M2=16, or M1=8 and M2=4, or M1=4 and M2=8;and

a feedback unit, configured to feed back the feedback report in aphysical uplink control channel.

The above terminal may further comprise the following features: whenM1=8 or M2=8, the 8 PMI1 indicate 0^(th), 2^(nd), 4^(th), 6^(th),8^(th), 10^(th), 12^(th) and 14^(th) codewords in the Rel-8 codebookrespectively.

The above terminal may further comprise the following features: whenM1=4 or M2=4, the 4 PMI1 indicate 0^(th), 4^(th), 8^(th) and 12^(th)codewords in the Rel-8 codebook respectively.

The above terminal may further comprise the following features: whenM1=4 or M2=4, the 4 PMI1 indicate 0^(th), 2^(nd), 4^(th) and 6^(th)codewords in the Rel-8 codebook respectively.

The above terminal may further comprise the following features: whenM1=M2, the M1 PMI1 are the same as the M2 PM2.

The above terminal may further comprise the following features: whenM1=M2, the M1 PMI1 are different from the M2 PM2.

The embodiments of the present invention further provide a terminal,comprising:

a channel state information acquisition unit, configured to acquirechannel state information, the channel state information comprising RankIndicator (RI) information, a second class of Precoding Matrix Indicator(PMI2) information, subband indication information, and channel qualityinformation; and

a feedback unit, configured to feed back the channel state informationin a physical uplink control channel, wherein, when RI=3 or 4, the PMI2information comprises 2 bits, and the PMI2 indicates one codeword in afirst set of codewords, and the first set of codewords comprises 4codewords selected from a codebook corresponding to Ranks 3 and 4 in theRel-8 codebook.

The above terminal may further comprise the following features: thefirst set of codewords comprise:

using 0^(th), 1^(st), 2^(nd), and 3^(rd) codewords of the codebookcorresponding to Ranks 3 and 4 in the Rel-8 codebook as a first group,using 8^(th), 9^(th), 10^(th), and 11^(th) codewords of the codebookcorresponding to Ranks 3 and 4 in the Rel-8 codebook as a second group,selecting 2 codewords from the first group and putting the 2 codewordsin the first set of codewords, and selecting 2 codewords from the secondgroup and putting the 2 codewords in the first set of codewords.

The above terminal may further comprise the following features: thefirst set of codewords comprises:

using 0^(th), 2^(nd), 8^(th), and 10^(th) codewords of the codebookcorresponding to Ranks 3 and 4 in the Rel-8 codebook as a third group,using 1^(st), 3^(rd), 9^(th), and 11^(th) codewords of the codebookcorresponding to Ranks 3 and 4 in the Rel-8 codebook as a fourth group,selecting 2 codewords from the third group and putting the 2 codewordsin the first set of codewords, and selecting 2 codewords from the fourthgroup and putting the 2 codewords in the first set of codewords.

The above terminal may further comprise the following features: thefirst set of codewords comprises:

using 0^(th), 2^(nd), 3^(rd), and 10^(th) codewords of the codebookcorresponding to Ranks 3 and 4 in the Rel-8 codebook as a fifth group,using 2^(nd), 8^(th), 9^(th), and 11^(th) codewords of the codebookcorresponding to Ranks 3 and 4 in the Rel-8 codebook as a sixth group,selecting 2 codewords from the fifth group and putting the 2 codewordsin the first set of codewords, and selecting 2 codewords from the sixthgroup and putting the 2 codewords in the first set of codewords.

The above terminal may further comprise the following features: thefirst set of codewords comprises:

using 0^(th), 1^(st), 2^(nd), and 9^(th) codewords of the codebookcorresponding to Ranks 3 and 4 in the Rel-8 codebook as a seventh group,using 3^(rd), 10^(th), 8^(th), and 11^(th) codewords of the codebookcorresponding to Ranks 3 and 4 in the Rel-8 codebook as an eighth group,selecting 2 codewords from the seventh group and putting the 2 codewordsin the first set of codewords, and selecting 2 codewords from the eighthgroup and putting the 2 codewords in the first set of codewords.

The above terminal may further comprise the following features: thefirst set of codewords comprises:

8^(th), 9^(th), 10^(th), and 11^(th) codewords of the codebookcorresponding to Ranks 3 and 4 in the Rel-8 codebook.

The above terminal may further comprise the following features: thefirst set of codewords comprises:

12^(th), 13^(th), 14^(th), and 15^(th) codewords of the codebookcorresponding to Ranks 3 and 4 in the Rel-8 codebook.

The above terminal may further comprise the following features: thefirst set of codewords comprises:

0^(th), 2^(nd), 12^(th), and 14^(th) codewords of the codebookcorresponding to Ranks 3 and 4 in the Rel-8 codebook.

The above terminal may further comprise the following features: thefirst set of codewords comprises:

4^(th), 5^(nd), 6^(th), and 7^(th) codewords of the codebookcorresponding to Ranks 3 and 4 in the Rel-8 codebook.

The above terminal may further comprise the following features: thefirst set of codewords comprises:

0^(th), 1^(st), 2^(nd), and 3rd codewords of the codebook correspondingto Ranks 3 and 4 in the Rel-8 codebook.

The above terminal may further comprise the following features: thefirst set of codewords comprises:

0^(th), 1^(st), 3rd, and 10^(th) codewords of the codebook correspondingto Ranks 3 and 4 in the Rel-8 codebook.

The above terminal may further comprise the following features: thefirst set of codewords comprises:

0^(th), 1^(st), 8^(th), and 11^(th) codewords of the codebookcorresponding to Ranks 3 and 4 in the Rel-8 codebook.

The above terminal may further comprise the following features: thefirst set of codewords comprises:

0^(th), 1^(st), 2^(nd), and 9^(th) codewords of the codebookcorresponding to Ranks 3 and 4 in the Rel-8 codebook.

The above terminal may further comprise the following features: thefirst set of codewords comprises:

1^(st), 3rd, 9^(th) and 11^(th) codewords of the codebook correspondingto Ranks 3 and 4 in the Rel-8 codebook.

The above terminal may further comprise the following features: thefirst set of codewords comprises:

0^(th), 2^(nd), 8^(th) and 10^(th) codewords of the codebookcorresponding to Ranks 3 and 4 in the Rel-8 codebook.

The above terminal may further comprise the following features: thefirst set of codewords comprises:

0^(th), 2^(nd), 3rd and 10^(th) codewords of the codebook correspondingto Ranks 3 and 4 in the Rel-8 codebook.

The above terminal may further comprise the following features: thefirst set of codewords comprises:

3rd, 8^(th), 10^(th) and 11^(th) codewords of the codebook correspondingto Ranks 3 and 4 in the Rel-8 codebook.

The above terminal may further comprise the following features: thefirst set of codewords comprises:

2^(nd), 9^(th), 8^(th), and 11^(th) codewords of the codebookcorresponding to Ranks 3 and 4 in the Rel-8 codebook.

The above terminal may further comprise the following features: thefirst set of codewords comprises:

2^(nd), 3^(rd), 9^(th), and 10^(th) codewords of the codebookcorresponding to Ranks 3 and 4 in the Rel-8 codebook.

The embodiments of the present invention further provide a terminal,comprising:

a channel state information acquisition unit, configured to acquirechannel state information, the channel state information comprising RankIndicator (RI) information, a second class of Precoding Matrix Indicator(PMI2) information, subband indication information, and channel qualityinformation; and

a feedback unit, configured to feed back the channel state informationin a physical uplink control channel, wherein, when RI=1 or 2, the PMI2information comprises 2 bits, and indicates one codeword in a second setof codewords, and the second set of codewords comprises:

0^(th), 1^(st), 2^(nd), and 3rd codewords in a codebook corresponding torank 1 in the Long Term Evolution-Advanced (LTE-A) Rel12 version or afirst or second codebook corresponding to rank 2 in the LTE-A Rel12version; or

0^(th), 1^(st), 8^(th), and 9^(th) codewords in a codebook correspondingto rank 1 in the LTE-A Rel12 version or a first or second codebookcorresponding to rank 2 in the LTE-A Rel12 version; or

0^(th), 4^(th), 8^(th), and 12^(th) codewords in a codebookcorresponding to rank 1 in the LTE-A Rel12 version or a first or secondcodebook corresponding to rank 2 in the LTE-A Rel12 version; or

0^(th), 4^(th), 5^(th), and 12^(th) codewords in a codebookcorresponding to rank 1 in the LTE-A Rel12 version or a first or secondcodebook corresponding to rank 2 in the LTE-A Rel12 version; or

0^(th), 1^(st), 4^(th), and 5^(th) codewords in a codebook correspondingto rank 1 in the LTE-A Rel12 version or a first or second codebookcorresponding to rank 2 in the LTE-A Rel12 version; or

12^(th), 13^(th), 14^(th), and 15^(th) codewords in a codebookcorresponding to rank 1 in the LTE-A Rel12 version or a first or secondcodebook corresponding to rank 2 in the LTE-A Rel12 version.

The embodiments of the present invention further provide a terminal,comprising:

a channel state information acquisition unit, configured to acquirechannel state information, the channel state information comprising RankIndicator (RI) information, a first class of Precoding Matrix Indicator(PMI1) information, and a second class of Precoding Matrix Indicator(PMI2) information; and

an encoding unit, configured to perform joint encoding on the PMI1information and the PMI2 information into a 4-bit feedback report,wherein,

the feedback report is used for indicating one of a set of combinationinformation formed by the PMI1 and the PMI2, and codewords indicated bythe set of combination information comprise codewords in a codebookcorresponding to Rank 1 or a first or second codebook corresponding toRank 2 in the Long Term Evolution-Advanced (LTE-A) Rel12 version; and

a feedback unit, configured to feed back the feedback report in aphysical uplink control channel.

The above terminal may further comprise the following features: whenRI=1, the codewords indicated by the set of combination informationcomprise codewords in the codebook corresponding to Rank 1 in the LTE-ARel12 version, and the codewords indicated by the set of combinationinformation meet:

complying with a model

${{\begin{bmatrix}u \\{e^{j\frac{m\;\pi}{4}} \cdot e^{j\frac{n\;\pi}{2}} \cdot u}\end{bmatrix}m} = 0},{{1\mspace{20mu} n} = 0},1,2,3,$wherein u is a 2-dimensional column vector.

The above terminal may further comprise the following features: thecodewords indicated by the set of combination information meet m=0; or

one half of the codewords indicated by the set of combinationinformation meet the model when m=0, and the other half of the codewordsindicated by the set of combination information meet the model when m=1;or

the codewords indicated by the set of combination information meet m=1.

The above terminal may further comprise the following features: a set ofcodewords indicated by the set of combination information is:

${{\begin{bmatrix}u_{i} \\{e^{j\;\theta_{i}}u_{i}}\end{bmatrix}i} = {0 \sim 15}},$wherein θ_(i) is any real number, and u_(i) is a 2-dimensional columnvector.

The above terminal may further comprise the following features:

${u_{i} \in \left\{ {\begin{bmatrix}1 \\1\end{bmatrix}\begin{bmatrix}1 \\{- 1}\end{bmatrix}} \right\}},$wherein in {u_(i), i=0˜15}, 8 values are

$\begin{bmatrix}1 \\1\end{bmatrix},$and 8 values are

$\begin{bmatrix}1 \\{- 1}\end{bmatrix}.$

The above terminal may further comprise the following features:

${u_{i} \in \left\{ {\begin{bmatrix}1 \\j\end{bmatrix}\begin{bmatrix}1 \\{- j}\end{bmatrix}} \right\}},$wherein, in {u_(i), i=0˜15}, 8 values are

$\begin{bmatrix}1 \\j\end{bmatrix},$and 8 values are

$\begin{bmatrix}1 \\{- j}\end{bmatrix}.$

The above terminal may further comprise the following features:

${u_{i} \in \left\{ {\begin{bmatrix}1 \\1\end{bmatrix}\mspace{14mu}\begin{bmatrix}1 \\j\end{bmatrix}} \right\}},$wherein, in {u_(i), i=0˜15}, 8 values are

$\begin{bmatrix}1 \\1\end{bmatrix},$and 8 values are.

$\begin{bmatrix}1 \\j\end{bmatrix}.$

The above terminal may further comprise the following features:

${u_{i} \in \left\{ {{{\begin{bmatrix}1 \\1\end{bmatrix}\mspace{14mu}\begin{bmatrix}1 \\{- 1}\end{bmatrix}}\mspace{14mu}\begin{bmatrix}1 \\j\end{bmatrix}}\mspace{14mu}\begin{bmatrix}1 \\{- j}\end{bmatrix}} \right\}},$wherein, in {u_(i), i=0˜15}, 4 values are

$\begin{bmatrix}1 \\1\end{bmatrix},$4 values are

$\begin{bmatrix}1 \\{- 1}\end{bmatrix},$4 values are

$\;{\begin{bmatrix}1 \\j\end{bmatrix},}$and 4 values are

$\;{\begin{bmatrix}1 \\{- j}\end{bmatrix}.}$

The above terminal may further comprise the following features:

${u_{i} \in \left\{ \;{{{{{{{\begin{bmatrix}1 \\1\end{bmatrix}\mspace{20mu}\begin{bmatrix}1 \\e^{j\frac{\pi}{4}}\end{bmatrix}}\mspace{20mu}\begin{bmatrix}1 \\j\end{bmatrix}}\mspace{20mu}\begin{bmatrix}1 \\e^{j\frac{3\pi}{4}}\end{bmatrix}}\mspace{20mu}\begin{bmatrix}1 \\{- 1}\end{bmatrix}}\mspace{20mu}\begin{bmatrix}1 \\e^{j\frac{5\pi}{4}}\end{bmatrix}}\mspace{14mu}\begin{bmatrix}1 \\{- j}\end{bmatrix}}\mspace{14mu}\begin{bmatrix}1 \\e^{j\frac{7\pi}{4}}\end{bmatrix}} \right\}},$wherein, in {u_(i), i=0˜15}, 2 values are

$\begin{bmatrix}1 \\1\end{bmatrix},$2 values are

$\begin{bmatrix}1 \\e^{j\frac{\pi}{4}}\end{bmatrix},$2 values are

$\begin{bmatrix}1 \\j\end{bmatrix},$2 values are

$\begin{bmatrix}1 \\e^{j\frac{3\pi}{4}}\end{bmatrix},$2 values are

$\begin{bmatrix}1 \\{- 1}\end{bmatrix},$2 values are

$\begin{bmatrix}1 \\e^{j\frac{5\pi}{4}}\end{bmatrix},$2 values are

$\begin{bmatrix}1 \\{- j}\end{bmatrix},$and 2 values are

$\begin{bmatrix}1 \\e^{j\frac{7\pi}{4}}\end{bmatrix}.$

The above terminal may further comprise the following features:

${u_{i} \in \begin{Bmatrix}\begin{bmatrix}1 \\1\end{bmatrix} & \begin{bmatrix}1 \\{- 1}\end{bmatrix} & \begin{bmatrix}1 \\j\end{bmatrix} & \begin{bmatrix}1 \\{- j}\end{bmatrix}\end{Bmatrix}},$wherein, in {u_(i), i=0˜15}, when 4 values of u_(i) are

$\begin{bmatrix}1 \\1\end{bmatrix},$m=0, when 4 values of u_(i) are

$\begin{bmatrix}1 \\{- 1}\end{bmatrix},$m=1, when 4 values of u_(i) are

$\begin{bmatrix}1 \\j\end{bmatrix},$m=0, and when 4 values of u_(i) are

$\begin{bmatrix}1 \\{- j}\end{bmatrix},$m=1.

The above terminal may further comprise the following features:

${u_{i} \in \begin{Bmatrix}\begin{matrix}\begin{bmatrix}1 \\1\end{bmatrix} & \begin{bmatrix}1 \\e^{j\frac{\pi}{4}}\end{bmatrix} & \begin{bmatrix}1 \\j\end{bmatrix} & \begin{bmatrix}1 \\e^{j\frac{3\pi}{4}}\end{bmatrix}\end{matrix} & \begin{bmatrix}1 \\{- 1}\end{bmatrix} & \begin{bmatrix}1 \\e^{j\frac{5\pi}{4}}\end{bmatrix} & \begin{bmatrix}1 \\{- j}\end{bmatrix} & \begin{bmatrix}1 \\e^{j\frac{7\pi}{4}}\end{bmatrix}\end{Bmatrix}},$wherein, in {u_(i), i=0˜15}, when 2 values of u_(i) are

$\begin{bmatrix}1 \\1\end{bmatrix},$m=0, when 2 values of u_(i) are

$\begin{bmatrix}1 \\e^{j\frac{\pi}{4}}\end{bmatrix},$m=0, when 2 values of u_(i) are

$\begin{bmatrix}1 \\j\end{bmatrix},$m=0, when 2 values of u_(i) are

$\begin{bmatrix}1 \\e^{j\frac{3\pi}{4}}\end{bmatrix},$m=0, when 2 values of u_(i) are

$\begin{bmatrix}1 \\{- 1}\end{bmatrix},$m=1, when 2 values of u_(i) are

$\begin{bmatrix}1 \\e^{j\frac{5\pi}{4}}\end{bmatrix},$m=1, when 2 values of u_(i) are

$\begin{bmatrix}1 \\{- j}\end{bmatrix},$m=1, and when 2 values of u_(i) are

$\begin{bmatrix}1 \\e^{j\frac{7\pi}{4}}\end{bmatrix},$m=1.

The above terminal may further comprise the following features: whenRI=2, codewords indicated by the set of combination information comprisecodewords of a first codebook corresponding to Rank2 in the LT-A Rel12version, and the codewords indicated by the set of combinationinformation comply with a model

${\begin{bmatrix}u_{i_{1}} & u_{i_{2}} \\{e^{j\;\theta_{m}}u_{i_{1}}} & {{- e^{j\;\theta_{m}}}u_{i_{2}}}\end{bmatrix}\mspace{14mu} i_{1}},i_{2},{m = {\left. 0 \right.\sim 15}},$wherein θ_(m) is any real number, and u_(i) is a 2-dimensional columnvector.

The above terminal may further comprise the following features: for alli₁ and i₂, i₁=i₂; or in the codewords, one half of the codewords meeti₂=i₁, and the other half of the codewords meet i₂≠i₁.

The above terminal may further comprise the following features:

$u_{i_{1}},{u_{i_{2}} \in \begin{Bmatrix}\begin{bmatrix}1 \\1\end{bmatrix} & \begin{bmatrix}1 \\{- 1}\end{bmatrix}\end{Bmatrix}},$wherein, in {u_(i) ₁ ,u_(i) ₂ , i=0˜15}, 8 values of u_(i) ₁ ,u_(i) ₂are

$\begin{bmatrix}1 \\1\end{bmatrix},$and 8 values of u_(i) ₁ ,u_(i) ₂ are

$\begin{bmatrix}1 \\{- 1}\end{bmatrix}_{\;}$respectively.

The above terminal may further comprise the following features:

$u_{i_{1}},{u_{i_{2}} \in \begin{Bmatrix}\begin{bmatrix}1 \\j\end{bmatrix} & \begin{bmatrix}1 \\{- j}\end{bmatrix}\end{Bmatrix}},$wherein, in {u_(i) ₁ ,u_(i) ₂ , i=0˜15}, 8 values of u_(i) ₁ ,u_(i) ₂are

$\begin{bmatrix}1 \\j\end{bmatrix},$and 8 values of u_(i) ₁ ,u_(i) ₂ are

$\quad\begin{bmatrix}1 \\{- j}\end{bmatrix}$respectively.

The above terminal may further comprise the following features:

$u_{i_{1}},{u_{i_{2}} \in \begin{Bmatrix}\begin{bmatrix}1 \\j\end{bmatrix} & \begin{bmatrix}1 \\1\end{bmatrix}\end{Bmatrix}},$wherein, in {u_(i) ₁ ,u_(i) ₂ , i=0˜15}, 8 values of u_(i) ₁ ,u_(i) ₂are

$\begin{bmatrix}1 \\1\end{bmatrix},$and 8 values of u_(i) ₁ ,u_(i) ₂ are

$\quad\begin{bmatrix}1 \\j\end{bmatrix}$respectively.

The above terminal may further comprise the following features:

$u_{i_{1}},{u_{i_{2}} \in \begin{Bmatrix}\begin{matrix}\begin{bmatrix}1 \\1\end{bmatrix} & \begin{bmatrix}1 \\{- 1}\end{bmatrix}\end{matrix} & \begin{bmatrix}1 \\j\end{bmatrix} & \begin{bmatrix}1 \\{- j}\end{bmatrix}\end{Bmatrix}},$wherein, in {u_(i) ₁ ,u_(i) ₂ , i=0˜15}, 6 values of u_(i) ₁ are

$\begin{bmatrix}1 \\1\end{bmatrix},$2 values of u_(i) ₁ are

$\begin{bmatrix}1 \\{- 1}\end{bmatrix},$6 values of u_(i) ₁ are

$\begin{bmatrix}1 \\j\end{bmatrix},$and 2 values of u_(i) ₁ are

$\begin{bmatrix}1 \\{- j}\end{bmatrix};$and 2 values of u_(i) ₁ are

$\begin{bmatrix}1 \\1\end{bmatrix},$4 values of u_(i) ₂ are

$\begin{bmatrix}1 \\{- 1}\end{bmatrix},$4 values of u_(i) ₂ are

$\begin{bmatrix}1 \\j\end{bmatrix},$and 6 values of u_(i) ₂ are

$\begin{bmatrix}1 \\{- j}\end{bmatrix}.$

The above terminal may further comprise the following features:

$u_{i_{1}},{u_{i_{2}} \in \left\{ {{{{{{{\begin{bmatrix}1 \\1\end{bmatrix}\mspace{14mu}\begin{bmatrix}1 \\e^{j\frac{\pi}{4}}\end{bmatrix}}\mspace{14mu}\begin{bmatrix}1 \\j\end{bmatrix}}\mspace{14mu}\begin{bmatrix}1 \\e^{j\frac{3\pi}{4}}\end{bmatrix}}\mspace{14mu}\begin{bmatrix}1 \\{- 1}\end{bmatrix}}\mspace{14mu}\begin{bmatrix}1 \\e^{j\frac{5\pi}{4}}\end{bmatrix}}\mspace{14mu}\begin{bmatrix}1 \\{- j}\end{bmatrix}}\mspace{14mu}\begin{bmatrix}1 \\e^{j\frac{7\pi}{4}}\end{bmatrix}} \right\}},$wherein, in {u_(i) ₁ ,u_(i) ₂ , i=0˜15}, 2 values of u_(i) ₁ ,u_(i) ₂are

$\begin{bmatrix}1 \\1\end{bmatrix},$2 values of u_(i) ₁ ,u_(i) ₂ are

$\begin{bmatrix}1 \\e^{j\frac{\pi}{4}}\end{bmatrix},$2 values of u_(i) ₁ ,u_(i) ₂ are

$\begin{bmatrix}1 \\j\end{bmatrix},$2 values of u_(i) ₁ ,u_(i) ₂ are

$\begin{bmatrix}1 \\e^{j\frac{3\pi}{4}}\end{bmatrix},$2 values of u_(i) ₁ ,u_(i) ₂ are

$\begin{bmatrix}1 \\{- 1}\end{bmatrix},$2 values of u_(i) ₁ ,u_(i) ₂ are

$\begin{bmatrix}1 \\e^{j\frac{5\pi}{4}}\end{bmatrix},$2 values of u_(i) ₁ ,u_(i) ₂ are

$\begin{bmatrix}1 \\{- j}\end{bmatrix},$and 2 values of u_(i) ₁ ,u_(i) ₂ in {u_(i) ₁ ,u_(i) ₂ , i=0˜15} are

$\quad\begin{bmatrix}1 \\e^{j\frac{7\pi}{4}}\end{bmatrix}$respectively.

The above terminal may further comprise the following features: whenRI=2, codewords indicated by the set of combination information comprisecodewords of a second codebook corresponding to Rank2 in the LTE-A Rel12version, and the codewords indicated by the set of combinationinformation comply with a model

${\begin{bmatrix}u_{i_{1}} & u_{i_{3}} \\{e^{j\;\theta_{m}}u_{i_{2}}} & {e^{j\;\theta_{n}}u_{i_{4}}}\end{bmatrix}\mspace{14mu} i_{1}},i_{2},i_{3},i_{4},m,{n = {0 \sim 15}},$wherein θ_(m),θ_(n) are any real numbers, and u_(i) is a 2-dimensionalcolumn vector.

The above terminal may further comprise the following features: for allthe u_(i) ₁ ,u_(i) ₂ ,u_(i) ₃ ,u_(i4), i₂=i₁=i₄=i₃; or

i₂=i₁ and i₄=i₃, and one half of the codewords indicated by the set ofcombination information meet i₂=i₁=i₄=i₃, and the other half of thecodewords meet i₁≠i₃; or

all codewords indicated by the set of combination information meet i₂=i₁and i₄=i₃, and the number of codewords which meet i₂=i₁=i₄=i₃ is morethan the number of codewords which meet i₁≠i₃; or

one half of codewords indicated by the set of combination informationmeet i₂=i₁=i₄=i₃, a quarter of the codewords meet i₂=i₁, i₄=i₃ andi₁≠i₃, and a quarter of the codewords meet i₁=i₄, i₂=i₃, and i₁≠i₂.

The embodiments of the present invention can reduce the overhead of thePMI feedback by joint encoding and can further ensure the accuracy ofthe PMI feedback with a limited overhead and obtain better precodingperformance.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram of a method for feeding back channel stateinformation according to an embodiment of the present invention;

FIG. 2 is a diagram of a method for feeding back channel stateinformation according to an embodiment of the present invention;

FIG. 3 is a diagram of a method for feeding back channel stateinformation according to an embodiment of the present invention;

FIG. 4 is a diagram of a method for feeding back channel stateinformation according to an embodiment of the present invention;

FIG. 5 is a block diagram of a terminal according to an embodiment ofthe present invention;

FIG. 6 is a block diagram of a terminal according to an embodiment ofthe present invention;

FIG. 7 is a block diagram of a terminal according to an embodiment ofthe present invention; and

FIG. 8 is a block diagram of a terminal according to an embodiment ofthe present invention.

PREFERRED EMBODIMENTS OF THE PRESENT INVENTION

The embodiments of the present invention will be described in detailbelow in conjunction with accompanying drawings. It should beillustrated that without a conflict, the embodiments in the presentapplication and the features in the embodiments can be combined witheach other randomly.

In addition, although a logical order is illustrated in the flowchart,in some cases, the steps illustrated or described can be performed in anorder different from here.

The embodiments of the present invention provide a method for feedingback channel state information, applied to a 4-antenna system,comprising:

a terminal acquiring channel information, the channel informationcomprising a first class of Precoding Matrix Indicator (PMI1)information and Rank Indicator (RI) information; the terminal performingjoint encoding on the PMI1 information and the RI information into a4-bit or 5-bit feedback report, wherein the feedback report is used forindicating one of a set of combination information formed by the RIinformation and the PMI1 information, and the set of combinationinformation comprises:

combination information of information of RI=1 with M1 PMI1respectively;

combination information of information of RI=2 with M2 PMI1respectively;

combination information of information of RI=3 with one PMI1;

combination information of information of RI=4 with one PMI1;

wherein M1=M2=4, or M1=16 and M2=8, or M1=8 and M2=16, or M1=16 andM2=4, or M1=4 and M2=16; and

the terminal feeding back the feedback report in a physical uplinkcontrol channel.

Alternatively, when RI=1 or RI=2, the 8 PMI1 indexes are 0^(th), 2^(nd),4^(th), 6^(th), 8^(th), 10^(th), 12^(th) and 14^(th) codewords;

alternatively, when RI=1 or RI=2, the 4 PMI1 indexes are 0^(th), 4^(th),8^(th) and 12^(th) codewords;

alternatively, when RI=1 or RI=2, the 4 PMI1 indexes are 0^(th), 2^(nd),4^(th) and 6^(th) codewords;

alternatively, the 4 PMI1 indexes respectively corresponding to theextracted codewords when RI=1 and when RI=2 are the same, such as 0, 2,4, 6, or 0, 4, 8, 12, or 0, 2, 4, 6, 8, 10, 12, 14;

alternatively, the 4 PMI1 indexes respectively corresponding to theextracted codewords when RI=1 and when RI=2 are not the same.

The embodiments of the present invention provide a method for feedingback channel state information, applied to a 4-antenna system,comprising: feeding back Rank Indicator (RI) information, a second classof Precoding Matrix Indicator (PMI2) information, subband indicationinformation, and channel quality information in a physical uplinkcontrol channel. When RI=3 or 4, the PMI2 information comprises 2 bits,and indicates one codeword in the set X of codewords. The set X ofcodewords comprises:

using 0^(th), 1^(st), 2^(nd), and 3^(rd) codewords in the Rel-8 codebookindicated by the PMI2 indexes as a first group, using 8^(th), 9^(th),10^(th), and 11^(th) codewords in the Rel-8 codebook indicated by thePMI2 indexes as a second group, and forming the 4 codewords by selecting2 codewords from the first group and selecting 2 codewords from thesecond group; wherein the Rel-8 codebook in the present disclosurerefers to the codebook defined in 3GPP TS 36.211 V8.9.0. Specifically,the 4 codewords indicated by the 4 PMI2 indexes are:

8^(th), 9^(th), 10^(th), and 11^(th) codewords in the Rel-8 Rank3,4codebook; or

12^(th), 13^(th), 14^(th), and 15^(th) codewords of the codebookcorresponding to Ranks 3 and 4 in the Rel-8 codebook; or

0^(th), 2^(nd), 12^(th), and 14^(th) codewords of the codebookcorresponding to Ranks 3 and 4 in the Rel-8 codebook; or

4^(th), 5^(nd), 6^(th), and 7^(th) codewords of the codebookcorresponding to Ranks 3 and 4 in the Rel-8 codebook; or

0^(th), 1^(st), 2^(nd), and 3^(rd) codewords in the codebookcorresponding to Ranks 3 and 4 in the Rel-8 codebook; or

0^(th), 1^(st), 3^(rd), and 10^(th) codewords in the codebookcorresponding to Ranks 3 and 4 in the Rel-8 codebook; or

0^(th), 1^(st), 8^(th), and 11^(th) codewords in the codebookcorresponding to Ranks 3 and 4 in the Rel-8 codebook; or

0^(th), 1^(st), 2^(nd) and 9^(th) codewords in the codebookcorresponding to Ranks 3 and 4 in the Rel-8 codebook; or

1^(st), 3^(rd), 9^(th) and 11^(th) codewords in the codebookcorresponding to Ranks 3 and 4 in the Rel-8 codebook; or

0^(th), 2^(nd), 8^(th) and 10^(th) codewords in the codebookcorresponding to Ranks 3 and 4 in the Rel-8 codebook.

Alternatively, using 0^(th), 2^(nd), 8^(th) and 10^(th) codewords in theRel-8 codebook indicated by the PMI2 indexes as a third group, using1^(st), 3^(rd), 9^(th), and 11^(th) codewords in the Rel-8 codebookindicated by the PMI2 indexes as a fourth group, and forming the 4codewords by selecting 2 codewords from the third group and selecting 2codewords from the fourth group.

Alternatively, the 4 PMI2 indexes indicate 0^(th), 1^(st), 3^(rd), and10^(th) codewords in the Rel-8 codebook.

Alternatively, the 4 PMI2 indexes indicate 3^(rd), 8^(th), 10^(th), and11^(th) codewords in the Rel-8 codebook.

Alternatively, the 4 PMI2 indexes indicate 2^(nd), 9^(th), 8^(th), and11^(th) codewords in the Rel-8 codebook.

Alternatively, using 0^(th), 2^(nd), 3^(rd) and 10^(th) codewords in theRel-8 codebook indicated by the PMI2 indexes as a fifth group, using2^(nd), 8^(th), 9^(th), and 11^(th) codewords in the Rel-8 codebookindicated by the PMI2 indexes as a sixth group, and forming the 4codewords by selecting 2 codewords from the fifth group and selecting 2codewords from the sixth group.

Alternatively, the 4 PMI2 indexes indicate 2^(nd), 3^(rd), 9^(th), and10^(th) codewords in the Rel-8 codebook.

Alternatively, using 0^(th), 1^(st), 2^(nd) and 9^(th) codewords in theRel-8 codebook indicated by the PMI2 indexes as a seventh group, using3^(rd), 10^(th), 8^(th), and 11^(th) codewords in the Rel-8 codebookindicated by the PMI2 indexes as an eighth group, and forming the 4codewords by selecting 2 codewords from the seventh group and selecting2 codewords from the eighth group.

The 4 codewords and the 8 codewords are actually selected by selectingsome elements from one large set to form one small set, which needs tohave a better quantization efficiency, so as to obtain betterperformance with minimum information and acquire the tradeoff betweenthe CSI quantization accuracy and the transmission link performance.

The embodiments of the present invention provide a method for feedingback channel state information, applied to a 4-antenna system,comprising: feeding back Rank Indicator (RI) information, a second classof Precoding Matrix Indicator (PMI2) information, subband indicationinformation, and channel quality information in a physical uplinkcontrol channel. When RI=1 or 2, the PMI2 comprises 2 bits, andindicates one codeword in a set X of codewords. The set X of codewordscomprises:

0^(th), 1^(st), 2^(nd), and 3^(rd) codewords in the codebook of thetable 4 or table 5-a or table 5-b indicated by the PMI2 indexes; or

0^(th), 1^(st), 8^(th), and 9^(th) codewords in the codebook of thetable 4 or table 5-a or table 5-b indicated by the PMI2 indexes; or

0^(th), 4^(th), 8^(th), and 12^(th) codewords in the codebook of thetable 4 or table 5-a or table 5-b indicated by the PMI2 indexes; or

0^(th), 4^(th), 5^(th), and 12^(th) codewords in the codebook of thetable 4 or table 5-a or table 5-b indicated by the PMI2 indexes; or

0^(th), 1^(st), 4^(th), and 5^(th) codewords in the codebook of thetable 4 or table 5-a or table 5-b indicated by the PMI2 indexes; or

12^(th), 13^(th), 14^(th), and 15^(th) codewords in the codebook of thetable 4 or table 5-a or table 5-b indicated by the PMI2 indexes.

The embodiments of the present invention provide a method for feedingback channel state information, applied to a 4-antenna system,comprising: feeding back Rank Indicator (RI) information, a first classof Precoding Matrix Indicator (PMI1) information, and a second class ofPrecoding Matrix Indicator (PMI2) information in the physical uplinkcontrol channel. When RI=1, the terminal performs joint encoding on thePMI1 information and the PMI2 information into a 4-bit feedback report,and the feedback report is used for indicating one of a set ofcombination information formed by the PMI1 and the PMI2, and the PMI1and the second PMI2 indicate codewords in the Rank1 codebook in theLTE-A Rel12 version; wherein the LTE-A Rel12 version in the presentdisclosure refers to 3GPP TS 36.213 V12.0.0. The codewords indicated bycombination information are:

the codewords complying with a model

${{\begin{bmatrix}u \\{e^{j\frac{m\;\pi}{4}} \cdot e^{j\frac{n\;\pi}{2}} \cdot u}\end{bmatrix}\mspace{14mu} m} = 0},{{1\mspace{14mu} n} = 0},1,2,3,$wherein u is a 2-dimensional column vector.

All codewords meet the model when m=0; or

one half of the codewords meet the model when m=0, and the other half ofthe codewords meet the model when m=1; or

all codewords fed back in the physical uplink control channel meet themodel when m=1.

A set of codewords corresponding to the set of combination informationof the PMI1 and the PMI2 is:

${{\begin{bmatrix}u_{i} \\{e^{j\;\theta_{i}}u_{i}}\end{bmatrix}\mspace{14mu} i} = {0 \sim 15}},$wherein θ_(i) is any real number, and u_(i) is a 2-dimensional columnvector.

${u_{i} \in \left\{ {\begin{bmatrix}1 \\1\end{bmatrix}\mspace{14mu}\begin{bmatrix}1 \\{- 1}\end{bmatrix}} \right\}},$wherein, in {u_(i), i=0˜15}, 8 values are

$\begin{bmatrix}1 \\1\end{bmatrix},$and 8 values are

${\begin{bmatrix}1 \\{- 1}\end{bmatrix};{{{or}\mspace{14mu} u_{i}} \in \left\{ {\begin{bmatrix}1 \\j\end{bmatrix}\begin{bmatrix}1 \\{- j}\end{bmatrix}} \right\}}},$wherein, in {u_(i), i=0˜15}, 8 values are

$\begin{bmatrix}1 \\j\end{bmatrix},$and 8 values are

${\begin{bmatrix}1 \\{- j}\end{bmatrix};{{{or}\mspace{14mu} u_{i}} \in \left\{ {\begin{bmatrix}1 \\1\end{bmatrix}\begin{bmatrix}1 \\j\end{bmatrix}} \right\}}},$wherein, in {u_(i), i=0˜15}, 8 values are

$\begin{bmatrix}1 \\1\end{bmatrix},$and 8 values are

${\begin{bmatrix}1 \\j\end{bmatrix};{{{or}\mspace{14mu} u_{i}} \in \left\{ {{{\begin{bmatrix}1 \\1\end{bmatrix}\begin{bmatrix}1 \\{- 1}\end{bmatrix}}\begin{bmatrix}1 \\j\end{bmatrix}}\begin{bmatrix}1 \\{- j}\end{bmatrix}} \right\}}},$wherein, in {u_(i), i=0˜15}, 4 values are

$\begin{bmatrix}1 \\1\end{bmatrix},$4 values are

$\begin{bmatrix}1 \\{- 1}\end{bmatrix},$4 values are

$\begin{bmatrix}1 \\j\end{bmatrix},$and 4 values are

${\begin{bmatrix}1 \\{- j}\end{bmatrix};{{{or}\mspace{14mu} u_{i}} \in \left\{ {{{{{{{\begin{bmatrix}1 \\1\end{bmatrix}\begin{bmatrix}1 \\e^{j\frac{\pi}{4}}\end{bmatrix}}\begin{bmatrix}1 \\j\end{bmatrix}}\begin{bmatrix}1 \\e^{j\frac{3\pi}{4}}\end{bmatrix}}\begin{bmatrix}1 \\{- 1}\end{bmatrix}}\begin{bmatrix}1 \\e^{j\frac{5\pi}{4}}\end{bmatrix}}\begin{bmatrix}1 \\{- j}\end{bmatrix}}\begin{bmatrix}1 \\e^{j\frac{7\pi}{4}}\end{bmatrix}} \right\}}},$wherein, in {u_(i), i=0˜15}, 2 values are

$\begin{bmatrix}1 \\1\end{bmatrix},$2 values are

$\begin{bmatrix}1 \\e^{j\frac{\pi}{4}}\end{bmatrix},$2 values are

$\begin{bmatrix}1 \\j\end{bmatrix},$2 values are

$\begin{bmatrix}1 \\e^{j\frac{3\pi}{4}}\end{bmatrix},$2 values are

$\begin{bmatrix}1 \\{- 1}\end{bmatrix},$2 values are

$\begin{bmatrix}1 \\e^{j\frac{5\pi}{4}}\end{bmatrix},$2 values are

$\begin{bmatrix}1 \\{- j}\end{bmatrix},$and 2 values are

$\begin{bmatrix}1 \\e^{j\frac{7\;\pi}{4}}\end{bmatrix}.$

Alternatively,

${u_{i} \in \left\{ {{{\begin{bmatrix}1 \\1\end{bmatrix}\begin{bmatrix}1 \\{- 1}\end{bmatrix}}\begin{bmatrix}1 \\j\end{bmatrix}}\begin{bmatrix}1 \\{- j}\end{bmatrix}} \right\}},$in {u_(i), i=0˜15}, when 4 values of u_(i) are

$\begin{bmatrix}1 \\1\end{bmatrix},$m=0, when 4 values of u_(i) are

$\begin{bmatrix}1 \\{- 1}\end{bmatrix},$m=1, when 4 values of u_(i) are

$\begin{bmatrix}1 \\j\end{bmatrix},$m=0, and when 4 values of u_(i) are

$\begin{bmatrix}1 \\{- j}\end{bmatrix},$m=1.

Alternatively,

${u_{i} \in \left\{ {{{{{{{\begin{bmatrix}1 \\1\end{bmatrix}\begin{bmatrix}1 \\e^{j\frac{\pi}{4}}\end{bmatrix}}\begin{bmatrix}1 \\j\end{bmatrix}}\begin{bmatrix}1 \\e^{j\frac{3\;\pi}{4}}\end{bmatrix}}\begin{bmatrix}1 \\{- 1}\end{bmatrix}}\begin{bmatrix}1 \\e^{j\frac{5\;\pi}{4}}\end{bmatrix}}\begin{bmatrix}1 \\{- j}\end{bmatrix}}\begin{bmatrix}1 \\e^{j\frac{7\;\pi}{4}}\end{bmatrix}} \right\}},$wherein, in {u_(i), i=0˜15}, when 2 values of u_(i) are

$\begin{bmatrix}1 \\1\end{bmatrix},$m=0, when 2 values of u_(i) are

$\begin{bmatrix}1 \\e^{j\frac{\pi}{4}}\end{bmatrix},$m=0, when 2 values of u_(i) are

$\begin{bmatrix}1 \\j\end{bmatrix},$m=0, when 2 values of u_(i) are

$\begin{bmatrix}1 \\e^{j\frac{3\;\pi}{4}}\end{bmatrix},$m=0, when 2 values of u_(i) are

$\begin{bmatrix}1 \\{- 1}\end{bmatrix},$m=1, when 2 values of u_(i) are

$\begin{bmatrix}1 \\e^{j\frac{5\;\pi}{4}}\end{bmatrix},$m=1, when 2 values of u_(i) are

$\begin{bmatrix}1 \\{- j}\end{bmatrix},$m=1, and when 2 values of u_(i) are

$\begin{bmatrix}1 \\e^{j\frac{7\pi}{4}}\end{bmatrix},$m=1.

When RI=2, the terminal performs joint encoding on the PMI1 informationand the PMI2 information into a 4-bit feedback report; the feedbackreport is used for indicating one of a set of combination informationformed by the PMI1 and the PMI2, and the PMI1 and the PMI2 indicatecodewords in the codebook of table 5-a of the Rank2 in the LTE-A Rel12version. The codewords indicated by combination information arecharacterized in that:

the codewords comply with a model

${\begin{bmatrix}u_{i_{1}} & u_{i_{2}} \\{e^{j\;\theta_{m}}u_{i_{1}}} & {{- e^{j\;\theta_{m}}}u_{i_{2}}}\end{bmatrix}\mspace{14mu} i_{1}},i_{2},{m = {0 \sim 15}},$wherein θ_(m) may be any real number, and u_(i) is a 2-dimensionalcolumn vector.

in the model, for all i₁ and i₂, i₁=i₂; or

in the codewords, one half of the codewords meet i₂=i₁, and the otherhalf of the codewords meet i₂≠i₁.

$u_{i_{1}},{u_{i_{2}} \in \left\{ {\begin{bmatrix}1 \\1\end{bmatrix}\mspace{14mu}\begin{bmatrix}1 \\{- 1}\end{bmatrix}} \right\}},$wherein, in {u_(i) ₁ ,u_(i) ₂ , i=0˜15}, 8 values of u_(i) ₁ ,u_(i) ₂are

$\begin{bmatrix}1 \\1\end{bmatrix},$and 8 values of u_(i) ₁ ,u_(i) ₂ are

$\begin{bmatrix}1 \\{- 1}\end{bmatrix}_{\;}$respectively; or

$u_{i_{1}},{u_{i_{2}} \in \left\{ {\begin{bmatrix}1 \\j\end{bmatrix}\mspace{14mu}\begin{bmatrix}1 \\{- j}\end{bmatrix}} \right\}},$wherein, in {u_(i) ₁ ,u_(i) ₂ , i=0˜15}, 8 values of u_(i) ₁ ,u_(i) ₂are

$\begin{bmatrix}1 \\j\end{bmatrix},$and 8 values of u_(i) ₁ ,u_(i) ₂ are

$\begin{bmatrix}1 \\{- j}\end{bmatrix}_{\;}$respectively; or

$u_{i_{1}},{u_{i_{2}} \in \left\{ {\begin{bmatrix}1 \\j\end{bmatrix}\mspace{14mu}\begin{bmatrix}1 \\1\end{bmatrix}} \right\}},$wherein, in {u_(i) ₁ ,u_(i) ₂ , i=0˜15}, 8 values of u_(i) ₁ ,u_(i) ₂are

$\begin{bmatrix}1 \\1\end{bmatrix},$and 8 values of u_(i) ₁ ,u_(i) ₂ are

$\begin{bmatrix}1 \\j\end{bmatrix}_{\;}$respectively; or

$u_{i_{1}},{u_{i_{2}} \in \left\{ {{{\begin{bmatrix}1 \\1\end{bmatrix}\mspace{14mu}\begin{bmatrix}1 \\{- 1}\end{bmatrix}}\mspace{14mu}\begin{bmatrix}1 \\j\end{bmatrix}}\mspace{14mu}\begin{bmatrix}1 \\{- j}\end{bmatrix}} \right\}},$wherein, in {u_(i) ₁ ,u_(i) ₂ , i=0˜15}, 6 values of u_(i) ₁ are

$\begin{bmatrix}1 \\1\end{bmatrix},$2 values of u_(i) ₁ are

$\begin{bmatrix}1 \\{- 1}\end{bmatrix},$6 values of u_(i) ₁ are

$\begin{bmatrix}1 \\j\end{bmatrix},$and 2 values of u_(i) ₁ are

$\begin{bmatrix}1 \\{- j}\end{bmatrix};$and 2 values of u_(i) ₂ are

$\begin{bmatrix}1 \\1\end{bmatrix},$4 values of u_(i) ₂ are

$\begin{bmatrix}1 \\{- 1}\end{bmatrix},$4 values of u_(i) ₂ are

$\begin{bmatrix}1 \\j\end{bmatrix},$and 6 values of u_(i) ₂ are

$\begin{bmatrix}1 \\{- j}\end{bmatrix};{or}$$u_{i_{1}},{u_{i_{2}} \in \left\{ {{{{{{{\begin{bmatrix}1 \\1\end{bmatrix}\begin{bmatrix}1 \\e^{j\frac{\;\pi}{4}}\end{bmatrix}}\begin{bmatrix}1 \\j\end{bmatrix}}\begin{bmatrix}1 \\e^{j\frac{3\;\pi}{4}}\end{bmatrix}}\begin{bmatrix}1 \\{- 1}\end{bmatrix}}\begin{bmatrix}1 \\e^{j\frac{5\;\pi}{4}}\end{bmatrix}}\begin{bmatrix}1 \\{- j}\end{bmatrix}}\begin{bmatrix}1 \\e^{j\frac{7\;\pi}{4}}\end{bmatrix}} \right\}},$wherein, in {u_(i) ₁ ,u_(i) ₂ , i=0˜15}, 2 values of u_(i) ₁ ,u_(i) ₂are

$\begin{bmatrix}1 \\1\end{bmatrix},$2 values of u_(i) ₁ ,u_(i) ₂ are

$\begin{bmatrix}1 \\e^{j\frac{\pi}{4}}\end{bmatrix},$2 values of u_(i) ₁ ,u_(i) ₂ are

$\begin{bmatrix}1 \\j\end{bmatrix},$2 values of u_(i) ₁ ,u_(i) ₂ are

$\begin{bmatrix}1 \\e^{j\frac{3\;\pi}{4}}\end{bmatrix},$2 values of u_(i) ₁ ,u_(i) ₂ are

$\begin{bmatrix}1 \\{- 1}\end{bmatrix},$2 values of u_(i) ₁ ,u_(i) ₂ are

$\begin{bmatrix}1 \\e^{j\frac{5\;\pi}{4}}\end{bmatrix},$2 values of u_(i) ₁ ,u_(i) ₂ are

$\begin{bmatrix}1 \\{- j}\end{bmatrix},$and 2 values of u_(i) ₁ ,u_(i) ₂ are

$\begin{bmatrix}1 \\e^{j\frac{7\;\pi}{4}}\end{bmatrix}\quad$respectively.

When RI=2, the terminal performs joint encoding on the PMI1 informationand the PMI2 information into a 4-bit feedback report; the feedbackreport is used for indicating one of a set of combination informationformed by the PMI1 and the PMI2, and the PMI1 and the PMI2 indicatecodewords in the Rank2-b codebook in the LTE-A Rel12 version. Thecodewords indicated by combination information are characterized inthat:

the codewords comply with a model

${\begin{bmatrix}u_{i_{1}} & u_{i_{3}} \\{e^{j\;\theta_{m}}u_{i_{2}}} & {{\mathbb{e}}^{j\;\theta_{n}}u_{i_{4}}}\end{bmatrix}\mspace{14mu} i_{1}},i_{2},i_{3},i_{4},m,{n = {0 \sim 15}},$wherein θ_(m),θ_(n) may be any real numbers, and u_(i) is a2-dimensional column vector.

For all the u_(i) ₁ ,u_(i) ₂ ,u_(i) ₃ ,u_(i) ₄ in the codeword model,i₂=i₁=i₄=i₃; or

all codewords meet i₂=i₁ and i₄=i₃, and one half of the codewords meeti₂=₁=i₄=i₃, and the other half of the codewords meet i₁≠i₃; or

all codewords meet i₂=i₁ and i₄=i₃, and the number of codewords whichmeet i₂=i₁=i₄=i₃ is more than the number of codewords which meet i₁≠i₃;or

one half of the codewords meet i₂=i₁=i₄=i₃, a quarter of the codewordsmeet i₂=i₁, i₄=i₃ and i₁≠i₃, and a quarter of the codewords meet i₁=i₄,i₂=i₃, and i₁≠i₂.

The embodiment provides a method for feeding back channel stateinformation. FIG. 1 is a first flowchart of the channel feedback methodaccording to the embodiment of the present invention. As shown in FIG.1, the method comprises the following steps.

In step S102, a terminal acquires channel state information, wherein thechannel state information comprises a first class of Precoding MatrixIndicator (PMI1) information and Rank Indicator (RI) information.

In step S104, the terminal performs joint encoding on the PMI1information and the RI information into a 5-bit feedback report.

In step S106, the terminal feeds back the feedback report in a physicaluplink control channel.

With the above steps, joint encoding is performed on the PMI1 and the RIin the channel state information, and the 5-bit feedback report isobtained and is fed back, which overcomes the problem in the related artthat the transmission performance of the system is poor due to a largeoverhead of the feedback channel information, reduces the overhead ofthe channel information feedback, and improves performance of a terminalfeeding back the channel information, thereby improving the transmissionperformance of the system. The above 5-bit feedback report is used forindicating one of a set of combination information formed by the RIinformation and the PMI1 information. The set comprises N elements,wherein N is more than 16 and less than or equal to 32.

Embodiment 1-1-1

Alternatively, the RI/PMI1 joint encoded set is shown in the followingtable 6:

TABLE 6 5 bits in total, information of RI and a part of i₁ 0-7  RI = 1:8 indexes of i₁ 8-15 RI = 2: 8 indexes of i₁ 16 RI = 3: 1 index of i₁ 17RI = 4: 1 index of i₁

Embodiment 1-1-2

Alternatively, the RI/PMI1 joint encoded set is shown in the followingtable 7:

TABLE 7 5 bits in total, information of RI and a part of i₁  0-15 RI =1: 16 indexes of i₁ 16-23 RI = 2: 8 indexes of i₁ 24 RI = 3: 1 index ofi₁ 25 RI = 4: 1 index of i₁ 26-31 Reserved

Embodiment 1-1-3

Alternatively, the RI/PMI1 joint encoded set is shown in the followingtable 8:

TABLE 8 5 bits in total, information of RI and a part of i₁ 0-7 RI = 1:8 indexes of i₁  8-23 RI = 2: 16 indexes of i₁ 24 RI = 3: 1 index of i₁25 RI = 4: 1 index of i₁ 26-31 Reserved

Alternatively, joint encoding may also be performed on the PMI1 and theRI in the channel information, and a 4-bit feedback report is obtainedand is fed back, which comprises the following steps, as shown in FIG.2.

In step S202, a terminal acquires channel state information, the channelstate information comprising PMI1 information and RI information.

In step S204, the terminal performs joint encoding on the PMI1information and the RI information into a 4-bit feedback report.

In step S206, the terminal feeds back the feedback report in a physicaluplink control channel.

The above 4-bit feedback report is used for indicating one of a set ofcombination information formed by the RI information and the PMI1. Theset comprises N elements, wherein N is more than 8 and less than orequal to 16.

The above steps overcome the problem in the related art that thetransmission performance of the system is poor due to a large overheadof the feedback channel information, reduces the overhead of the channelinformation feedback, and improves performance of a terminal feedingback the channel information, thereby improving the transmissionperformance of the system. The N elements are actually selected byselecting some elements from one large set to form one small set, whichneeds to have a better quantization efficiency, so as to obtain betterperformance with minimum information and acquire the tradeoff betweenthe CSI quantization accuracy and the transmission link performance.

The following is specific embodiments when codewords are extractedspecifically.

Embodiment 1-1

The joint encoding table is as follows:

TABLE 9 I_(RI/PMI1) RI Codebook index i₁ 0-3 1 0, 4, 8, 12 4-7 2 0, 4,8, 12 8 3 0 9 4 0 10-15 Reserved NA

Values of a joint encoding table are as follows: by taking a first rowas an example, when the value of the feedback report is 0, RI=1 andi₁=0; when the value of the feedback report is 1, RI=1 and i₁=4; whenthe value of the feedback report is 2, RI=1 and i₁=8; and when the valueof the feedback report is 3, RI=1 and i₁=12.

Embodiment 1-2

The joint encoding table is as follows:

TABLE 10 I_(RI/PMI1) RI Codebook index i₁ 0-3 1 0, 2, 4, 6 4-7 2 0, 2,4, 6 8 3 0 9 4 0 10-15 Reserved NA

Embodiment 1-3

The joint encoding table is as follows:

TABLE 11 I_(RI/PMI1) RI Codebook index i₁ 0-7 1 0, 2, 4, 6, 8, 10, 12,14  8-15 2 0, 2, 4, 6, 8, 10, 12, 14 16 3 0 17 4 0 18-31 Reserved NA

Embodiment 1-4

The joint encoding table is as follows:

TABLE 12 I_(RI/PMI1) RI Codebook index i₁  0-15 1 0-15 16-23 2 0, 2, 4,6, 8, 10, 12, 14 24 3 0 25 4 0 26-31 Reserved NA

Embodiment 1-5

The joint encoding table is as follows:

TABLE 13 I_(RI/PMI1) RI Codebook index i₁ 0-7 1 0, 2, 4, 6, 8, 10, 12,14  8-23 2 0-15 24 3 0 25 4 0 26-31 Reserved NA

Embodiment 1-6

The joint encoding table is as follows:

TABLE 14 I_(RI/PMI1) RI Codebook index i₁ 0-3 1 0, 4 , 8, 12 4-7 2 0, 2,4, 6 8 3 0 9 4 0 10-15 Reserved NA

Embodiment 1-7

The joint encoding table is as follows:

TABLE 15 I_(RI/PMI1) RI Codebook index i₁ 0-3 1 0, 2, 4, 6 4-7 2 0, 4,8, 12 8 3 0 9 4 0 10-15 Reserved NA

Embodiment 1-8

The joint encoding table is as follows:

TABLE 16 I_(RI/PMI1) RI Codebook index i₁ 0-7 1 0, 2, 4, 6, 8, 10, 12,14  8-11 2 0, 4, 8, 12 12 3 0 13 4 0 14-15 Reserved NA

Embodiment 1-9

The joint encoding table is as follows:

TABLE 17 I_(RI/PMI1) RI Codebook index i₁ 0-3 1 0, 2, 4, 6  4-11 2 0, 2,4, 6, 8, 10, 12, 14 12 3 0 13 4 0 14-15 Reserved NA

Embodiment 1-10

The joint encoding table is as follows:

TABLE 18 I_(RI/PMI1) RI Codebook index i₁ 0-7 1 0, 2, 4, 6, 8, 10, 12,14  8-11 2 0, 2, 4, 6 12 3 0 13 4 0 14-15 Reserved NA

Embodiment 1-11

The joint encoding table is as follows:

TABLE 19 I_(RI/PMI1) RI Codebook index i₁ 0-3 1 0, 4, 8, 12  4-11 2 0,2, 4, 6, 8, 10, 12, 14 12 3 0 13 4 0 14-15 Reserved NA

The embodiment provides a method for feeding back channel stateinformation, which comprises the following steps, as shown in FIG. 3.

In step S302, a terminal acquires channel information, the channelinformation comprising a first class of Precoding Matrix Indicator(PMI1) information and a second class of Precoding Matrix Indicator(PMI2) information.

In step S304, the terminal performs joint encoding on the PMI1information and the PMI2 information into a 4-bit feedback report.

In step S306, the terminal feeds back the feedback report in a physicaluplink control channel.

With the method, the overhead of the PMI1 and the PMI2 can beeffectively reduced, and it can be ensured that the performance will notbe reduced significantly.

The 4-bit feedback report corresponds to 16 combinations of the PMI1 andthe PMI2. The combination of the PMI1 and the PMI2 corresponds tocodewords in the LTE-A Rel 12.

When RI=1, the embodiment is described as follows.

Embodiment 2-1-1

TABLE 20 Relationship between PMI1 and Relationship between PMI2 thecodebook index i₁ and the codebook index i₂ RI I_(PMI1) Codebook indexi₁ I_(PMI2) Codebook index i₂ 1 0-3 0, 4, 8, 12 0-3 0, 2, 9, 11/0, 2, 8,10

Embodiment 2-1-2

TABLE 21 Relationship between PMI1 and Relationship between PMI2 and thethe codebook index i₁ codebook index i₂ RI I_(PMI1) Codebook index i₁I_(PMI2) Codebook index i₂ 1 0-1 0, 4 0-7 0, 2, 4, 6, 9, 11, 13, 15/ 0,2, 4, 6, 8, 10, 12, 14/0, 1, 2, 3, 8, 9, 10, 11

Embodiment 2-1-3

TABLE 22 Relationship between PMI1 and Relationship between PMI2 thecodebook index i₁ and the codebook index i₂ RI I_(PMI1) Codebook indexi₁ I_(PMI2) Codebook index i₂ 1 0-1 0, 8 0-7 0, 1, 2, 3, 8, 9, 10, 11

Embodiment 2-1-4

TABLE 23 Relationship between PMI1 and Relationship between PMI2 thecodebook index i₁ and the codebook index i₂ RI I_(PMI1) Codebook indexi₁ I_(PMI1) Codebook index i₂ 1 0-1 0, 8 0-7 0, 1, 2, 3, 8, 9, 10, 11

Embodiment 2-1-5

TABLE 24 Relationship between PMI1 and Relationship between PMI2 thecodebook index i₁ and the codebook index i₂ RI I_(PMI1) Codebook indexi₁ I_(PMI2) Codebook index i₂ 1 0 0 0-15 0-15

For the condition of Rank2, the embodiment is described as follows.

Embodiment 2-2-1

TABLE 25 Relationship between PMI1 and Relationship between PMI2 thecodebook index i₁ and the codebook index i₂ RI I_(PMI1) Codebook indexi₁ I_(PMI2) Codebook index i₂ 2 0 0 0-15 0-15

Embodiment 2-2-2

TABLE 26 Relationship between PMI1 and Relationship between PMI2 thecodebook index i₁ and the codebook index i₂ RI I_(PMI1) Codebook indexi₁ I_(PMI2) Codebook index i₂ 2 0 8 0-15 0-15

Embodiment 2-2-3

TABLE 27 Relationship between PMI1 and Relationship between PMI2 thecodebook index i₁ and the codebook index i₂ RI I_(PMI1) Codebook indexi₁ I_(PMI2) Codebook index i₂ 2 0-1 0, 4 0-7 0, 1, 2, 3, 4, 5, 6, 7

The embodiments of the present invention further provide a method forfeeding back channel state information, which comprises the followingsteps, as shown in FIG. 4.

In step S401, a terminal acquires channel information, wherein thechannel information at least comprises a second class of PrecodingMatrix Indicator (PMI2) information and Channel Quality Information(CQI) corresponding to a subband and subband position indicationinformation; and the terminal generates a feedback report and the PMI2occupies 2 bits;

In step S403, the terminal feeds back the feedback report in thephysical uplink control channel.

With the above steps, when a subband PMI2 is fed back, some codewordsonly are extracted from the original codebook to form a new codebook forquantizing the feedback; and during Ranks 3 and 4, the overheadcorresponding to the feedback of the subband PMI2 is merely 2 bits, andthe corresponding 4 codewords are described in the followingembodiments.

Embodiment 3-1

When the codewords included in the Rank3,4 codebook are codewords in theRel-8 Rank3,4 codebook illustrated in table 2, preferably, the 4codewords extracted therefrom may be as follows.

TABLE 28 Rank3 Rank4 codewords codewords 0 PMI2 is 0$\quad\begin{bmatrix}1 & 1 & 1 \\1 & 1 & {- 1} \\1 & {- 1} & {- 1} \\1 & {- 1} & 1\end{bmatrix}$ $\quad\begin{bmatrix}1 & 1 & 1 & 1 \\1 & 1 & {- 1} & {- 1} \\1 & {- 1} & 1 & {- 1} \\1 & {- 1} & {- 1} & 1\end{bmatrix}$ 1 PMI2 is 1 $\quad\begin{bmatrix}1 & {- j} & {- 1} \\j & 1 & j \\{- 1} & {- j} & 1 \\{- j} & 1 & {- j}\end{bmatrix}$ $\quad\begin{bmatrix}1 & {- j} & {- 1} & j \\j & 1 & j & 1 \\{- 1} & {- j} & 1 & j \\{- j} & 1 & {- j} & 1\end{bmatrix}$ 2 PMI2 is 2 $\quad\begin{bmatrix}1 & {- 1} & 1 \\{- 1} & 1 & 1 \\1 & 1 & 1 \\{- 1} & {- 1} & 1\end{bmatrix}$ $\quad\begin{bmatrix}1 & {- 1} & 1 & {- 1} \\1 & 1 & {- 1} & {- 1} \\1 & 1 & 1 & 1 \\1 & {- 1} & {- 1} & 1\end{bmatrix}$ 3 PMI2 is 9 $\quad\begin{bmatrix}1 & 1 & {- j} \\j & {- j} & {- 1} \\1 & 1 & j \\j & {- j} & 1\end{bmatrix}$ $\quad\begin{bmatrix}1 & {- j} & 1 & {- j} \\j & 1 & {- j} & {- 1} \\1 & j & 1 & j \\j & {- 1} & {- j} & 1\end{bmatrix}$

Embodiment 3-2

When the codewords included in the Rank3,4 codebook are codewords in theRel-8 Rank3,4 codebook illustrated in table 2, preferably, the 4codewords extracted therefrom may be as follows.

TABLE 29 Rank3 Rank4 codewords codewords 0 PMI2 is 1$\quad\begin{bmatrix}1 & {- j} & {- 1} \\j & 1 & j \\{- 1} & {- j} & 1 \\{- j} & 1 & {- j}\end{bmatrix}$ $\quad\begin{bmatrix}1 & {- j} & {- 1} & j \\j & 1 & j & 1 \\{- 1} & {- j} & 1 & j \\{- j} & 1 & {- j} & 1\end{bmatrix}$ 1 PMI2 is 3 $\quad\begin{bmatrix}1 & j & {- 1} \\{- j} & 1 & {- j} \\{- 1} & j & 1 \\j & 1 & j\end{bmatrix}$ $\quad\begin{bmatrix}1 & j & {- 1} & {- j} \\{- j} & 1 & {- j} & 1 \\{- 1} & j & 1 & {- j} \\j & 1 & j & 1\end{bmatrix}$ 2 PMI2 is 9 $\quad\begin{bmatrix}1 & 1 & {- j} \\j & {- j} & {- 1} \\1 & 1 & j \\j & {- j} & 1\end{bmatrix}$ $\quad\begin{bmatrix}1 & {- j} & 1 & {- j} \\j & 1 & {- j} & {- 1} \\1 & j & 1 & j \\j & {- 1} & {- j} & 1\end{bmatrix}$ 3 PMI2 is 11 $\quad\begin{bmatrix}1 & 1 & j \\{- j} & j & {- 1} \\1 & 1 & {- j} \\{- j} & j & 1\end{bmatrix}$ $\quad\begin{bmatrix}1 & j & 1 & j \\{- j} & 1 & j & {- 1} \\1 & {- j} & 1 & {- j} \\{- j} & {- 1} & j & 1\end{bmatrix}$

Embodiment 3-3

When the codewords included in the Rank3,4 codebook are codewords in theRel-8 Rank3,4 codebook illustrated in table 2, preferably, the 4codewords extracted therefrom may be as follows.

TABLE 30 Rank3 Rank4 codewords codewords 0 PMI2 is 0$\quad\begin{bmatrix}1 & 1 & 1 \\1 & 1 & {- 1} \\1 & {- 1} & {- 1} \\1 & {- 1} & 1\end{bmatrix}$ $\quad\begin{bmatrix}1 & 1 & 1 & 1 \\1 & 1 & {- 1} & {- 1} \\1 & {- 1} & 1 & {- 1} \\1 & {- 1} & {- 1} & 1\end{bmatrix}$ 1 PMI2 is 2 $\quad\begin{bmatrix}1 & {- 1} & 1 \\{- 1} & 1 & 1 \\1 & 1 & 1 \\{- 1} & {- 1} & 1\end{bmatrix}$ $\quad\begin{bmatrix}1 & {- 1} & 1 & {- 1} \\1 & 1 & {- 1} & {- 1} \\1 & 1 & 1 & 1 \\1 & {- 1} & {- 1} & 1\end{bmatrix}$ 2 PMI2 is 8 $\quad\begin{bmatrix}1 & 1 & {- 1} \\1 & 1 & 1 \\{- 1} & 1 & {- 1} \\{- 1} & 1 & 1\end{bmatrix}$ $\quad\begin{bmatrix}1 & 1 & {- 1} & {- 1} \\1 & 1 & 1 & 1 \\{- 1} & 1 & 1 & {- 1} \\{- 1} & 1 & {- 1} & 1\end{bmatrix}$ 3 PMI2 is 10 $\quad\begin{bmatrix}1 & {- 1} & {- 1} \\{- 1} & 1 & {- 1} \\{- 1} & {- 1} & 1 \\1 & 1 & 1\end{bmatrix}$ $\quad\begin{bmatrix}1 & {- 1} & {- 1} & 1 \\{- 1} & {- 1} & 1 & 1 \\{- 1} & 1 & {- 1} & 1 \\1 & 1 & 1 & 1\end{bmatrix}$

Embodiment 3-4

When the codewords included in the Rank3,4 codebook are codewords in theRel-8 Rank3,4 codebook illustrated in table 2, preferably, the 4codewords extracted therefrom may be as follows.

TABLE 31 Rank3 Rank4 codewords codewords 0 PMI2 is 0$\quad\begin{bmatrix}1 & 1 & 1 \\1 & 1 & {- 1} \\1 & {- 1} & {- 1} \\1 & {- 1} & 1\end{bmatrix}$ $\quad\begin{bmatrix}1 & 1 & 1 & 1 \\1 & 1 & {- 1} & {- 1} \\1 & {- 1} & 1 & {- 1} \\1 & {- 1} & {- 1} & 1\end{bmatrix}$ 1 PMI2 is 1 $\quad\begin{bmatrix}1 & {- j} & {- 1} \\j & 1 & j \\{- 1} & {- j} & 1 \\{- j} & 1 & {- j}\end{bmatrix}$ $\quad\begin{bmatrix}1 & {- j} & {- 1} & j \\j & 1 & j & 1 \\{- 1} & {- j} & 1 & j \\{- j} & 1 & {- j} & 1\end{bmatrix}$ 2 PMI2 is 3 $\quad\begin{bmatrix}1 & j & {- 1} \\{- j} & 1 & {- j} \\{- 1} & j & 1 \\j & 1 & j\end{bmatrix}$ $\quad\begin{bmatrix}1 & j & {- 1} & {- j} \\{- j} & 1 & {- j} & 1 \\{- 1} & j & 1 & {- j} \\j & 1 & j & 1\end{bmatrix}$ 3 PMI2 is 10 $\quad\begin{bmatrix}1 & {- 1} & {- 1} \\{- 1} & 1 & {- 1} \\{- 1} & {- 1} & 1 \\1 & 1 & 1\end{bmatrix}$ $\quad\begin{bmatrix}1 & {- 1} & {- 1} & 1 \\{- 1} & {- 1} & 1 & 1 \\{- 1} & 1 & {- 1} & 1 \\1 & 1 & 1 & 1\end{bmatrix}$

Embodiment 3-5

When the codewords included in the Rank3,4 codebook are codewords in theRel-8 Rank3,4 codebook illustrated in table 2, preferably, the 4codewords extracted therefrom may be as follows.

TABLE 32 Rank3 Rank4 codewords codewords 0 PMI2 is 2$\quad\begin{bmatrix}1 & {- 1} & 1 \\{- 1} & 1 & 1 \\1 & 1 & 1 \\{- 1} & {- 1} & 1\end{bmatrix}$ $\quad\begin{bmatrix}1 & {- 1} & 1 & {- 1} \\1 & 1 & {- 1} & {- 1} \\1 & 1 & 1 & 1 \\1 & {- 1} & {- 1} & 1\end{bmatrix}$ 1 PMI2 is 8 $\quad\begin{bmatrix}1 & 1 & {- 1} \\1 & 1 & 1 \\{- 1} & 1 & {- 1} \\{- 1} & 1 & 1\end{bmatrix}$ $\quad\begin{bmatrix}1 & 1 & {- 1} & {- 1} \\1 & 1 & 1 & 1 \\{- 1} & 1 & 1 & {- 1} \\{- 1} & 1 & {- 1} & 1\end{bmatrix}$ 2 PMI2 is 9 $\quad\begin{bmatrix}1 & 1 & {- j} \\j & {- j} & {- 1} \\1 & 1 & j \\j & {- j} & 1\end{bmatrix}$ $\quad\begin{bmatrix}1 & {- j} & 1 & {- j} \\j & 1 & {- j} & {- 1} \\1 & j & 1 & j \\j & {- 1} & {- j} & 1\end{bmatrix}$ 3 PMI2 is 11 $\quad\begin{bmatrix}1 & 1 & j \\{- j} & j & {- 1} \\1 & 1 & {- j} \\{- j} & j & 1\end{bmatrix}$ $\quad\begin{bmatrix}1 & 1 & j & j \\{- j} & j & 1 & {- 1} \\1 & 1 & {- j} & {- j} \\{- j} & j & {- 1} & 1\end{bmatrix}$

Embodiment 3-6

When the codewords included in the Rank3,4 codebook are codewords in theRel-8 Rank3,4 codebook illustrated in table 2, preferably, the 4codewords extracted therefrom may be as follows.

TABLE 33 Rank3 Rank4 codewords codewords 0 PMI2 is 2$\quad\begin{bmatrix}1 & {- 1} & 1 \\{- 1} & 1 & 1 \\1 & 1 & 1 \\{- 1} & {- 1} & 1\end{bmatrix}$ $\quad\begin{bmatrix}1 & {- 1} & 1 & {- 1} \\1 & 1 & {- 1} & {- 1} \\1 & 1 & 1 & 1 \\1 & {- 1} & {- 1} & 1\end{bmatrix}$ 1 PMI2 is 3 $\quad\begin{bmatrix}1 & j & {- 1} \\{- j} & 1 & {- j} \\{- 1} & j & 1 \\j & 1 & j\end{bmatrix}$ $\quad\begin{bmatrix}1 & j & {- 1} & {- j} \\{- j} & 1 & {- j} & 1 \\{- 1} & j & 1 & {- j} \\j & 1 & j & 1\end{bmatrix}$ 2 PMI2 is 9 $\quad\begin{bmatrix}1 & 1 & {- j} \\j & {- j} & {- 1} \\1 & 1 & j \\j & {- j} & 1\end{bmatrix}$ $\quad\begin{bmatrix}1 & {- j} & 1 & {- j} \\j & 1 & {- j} & {- 1} \\1 & j & 1 & j \\j & {- 1} & {- j} & 1\end{bmatrix}$ 3 PMI2 is 10 $\quad\begin{bmatrix}1 & {- 1} & {- 1} \\{- 1} & 1 & {- 1} \\{- 1} & {- 1} & 1 \\1 & 1 & 1\end{bmatrix}$ $\quad\begin{bmatrix}1 & {- 1} & {- 1} & 1 \\{- 1} & {- 1} & 1 & 1 \\{- 1} & 1 & {- 1} & 1 \\1 & 1 & 1 & 1\end{bmatrix}$

Embodiment 3-7

When the codewords included in the Rank3,4 codebook are codewords in theRel-8 Rank3,4 codebook illustrated in table 2, preferably, the 4codewords extracted therefrom may be as follows.

TABLE 34 Rank3 Rank4 codewords codewords 0 PMI2 is 0$\quad\begin{bmatrix}1 & 1 & 1 \\1 & 1 & {- 1} \\1 & {- 1} & {- 1} \\1 & {- 1} & 1\end{bmatrix}$ $\quad\begin{bmatrix}1 & 1 & 1 & 1 \\1 & 1 & {- 1} & {- 1} \\1 & {- 1} & 1 & {- 1} \\1 & {- 1} & {- 1} & 1\end{bmatrix}$ 1 PMI2 is 1 $\quad{\quad\begin{bmatrix}1 & {- j} & {- 1} \\j & 1 & j \\{- 1} & {- j} & 1 \\j & 1 & {- j}\end{bmatrix}}$ $\quad\begin{bmatrix}1 & {- j} & {- 1} & j \\j & 1 & j & 1 \\{- 1} & {- j} & 1 & j \\{- j} & 1 & {- j} & 1\end{bmatrix}$ 2 PMI2 is 2 $\quad\begin{bmatrix}1 & {- 1} & 1 \\{- 1} & 1 & 1 \\1 & 1 & 1 \\{- 1} & {- 1} & 1\end{bmatrix}$ $\quad\begin{bmatrix}1 & {- 1} & 1 & {- 1} \\1 & 1 & {- 1} & {- 1} \\1 & 1 & 1 & 1 \\1 & {- 1} & {- 1} & 1\end{bmatrix}$ 3 PMI2 is 3 $\quad\begin{bmatrix}1 & j & {- 1} \\{- j} & 1 & {- j} \\{- 1} & j & 1 \\j & 1 & j\end{bmatrix}$ $\quad\begin{bmatrix}1 & j & {- 1} & {- j} \\{- j} & 1 & {- j} & 1 \\{- 1} & j & 1 & {- j} \\j & 1 & j & 1\end{bmatrix}$

Embodiment 3-8

When the codewords included in the Rank3,4 codebook are codewords in theRel-8 Rank3,4 codebook illustrated in table 2, preferably, the 4codewords extracted therefrom may be as follows.

TABLE 35 Rank3 Rank4 codewords codewords 0 PMI2 is 8$\quad\begin{bmatrix}1 & 1 & {- 1} \\1 & 1 & 1 \\{- 1} & 1 & {- 1} \\{- 1} & 1 & 1\end{bmatrix}$ $\quad\begin{bmatrix}1 & 1 & {- 1} & {- 1} \\1 & 1 & 1 & 1 \\{- 1} & 1 & 1 & {- 1} \\{- 1} & 1 & {- 1} & 1\end{bmatrix}$ 1 PMI2 is 9 $\quad\begin{bmatrix}1 & 1 & {- j} \\j & {- j} & {- 1} \\1 & 1 & j \\j & {- j} & 1\end{bmatrix}$ $\quad\begin{bmatrix}1 & {- j} & 1 & {- j} \\j & 1 & {- j} & {- 1} \\1 & j & 1 & j \\j & {- 1} & {- j} & 1\end{bmatrix}$ 2 PMI2 is 10 $\quad\begin{bmatrix}1 & {- 1} & {- 1} \\{- 1} & 1 & {- 1} \\{- 1} & {- 1} & 1 \\1 & 1 & 1\end{bmatrix}$ $\quad\begin{bmatrix}1 & {- 1} & {- 1} & 1 \\{- 1} & {- 1} & 1 & 1 \\{- 1} & 1 & {- 1} & 1 \\1 & 1 & 1 & 1\end{bmatrix}$ 3 PMI2 is 11 $\quad\begin{bmatrix}1 & 1 & j \\{- j} & j & {- 1} \\1 & 1 & {- j} \\{- j} & j & 1\end{bmatrix}$ $\quad\begin{bmatrix}1 & 1 & j & j \\{- j} & j & 1 & {- 1} \\1 & 1 & {- j} & {- j} \\{- j} & j & {- 1} & 1\end{bmatrix}$

Embodiment 3-9

When the codewords included in the Rank3,4 codebook are codewords in theRel-8 Rank3,4 codebook illustrated in table 2, preferably, the 4codewords extracted therefrom may be as follows.

TABLE 36 Rank3 Rank4 codewords codewords 0 PMI2 is 12$\quad\begin{bmatrix}1 & 1 & 1 \\1 & 1 & {- 1} \\1 & {- 1} & 1 \\{- 1} & 1 & 1\end{bmatrix}$ $\quad\begin{bmatrix}1 & 1 & 1 & {- 1} \\1 & 1 & {- 1} & 1 \\1 & {- 1} & 1 & 1 \\{- 1} & 1 & 1 & 1\end{bmatrix}$ 1 PMI2 is 13 $\quad\begin{bmatrix}1 & 1 & {- 1} \\1 & 1 & 1 \\{- 1} & 1 & 1 \\1 & {- 1} & 1\end{bmatrix}$ $\quad\begin{bmatrix}1 & 1 & {- 1} & 1 \\1 & 1 & 1 & {- 1} \\{- 1} & 1 & 1 & 1 \\1 & {- 1} & 1 & 1\end{bmatrix}$ 2 PMI2 is 14 $\quad\begin{bmatrix}1 & {- 1} & 1 \\{- 1} & 1 & 1 \\1 & 1 & 1 \\1 & 1 & {- 1}\end{bmatrix}$ $\quad\begin{bmatrix}1 & {- 1} & 1 & 1 \\1 & 1 & {- 1} & 1 \\1 & 1 & 1 & {- 1} \\{- 1} & 1 & 1 & 1\end{bmatrix}$ 3 PMI2 is 15 $\quad\begin{bmatrix}1 & {- 1} & {- 1} \\{- 1} & 1 & {- 1} \\{- 1} & {- 1} & 1 \\{- 1} & {- 1} & {- 1}\end{bmatrix}$ $\quad\begin{bmatrix}1 & {- 1} & {- 1} & {- 1} \\{- 1} & 1 & {- 1} & {- 1} \\{- 1} & {- 1} & 1 & {- 1} \\{- 1} & {- 1} & {- 1} & 1\end{bmatrix}$

The codebooks obtained by multiplying the codewords of Rank1, Rank2,Rank3, and Rank4 by any non-zero complex number are equivalent to thecodebooks before the change.

The codebooks formed by performing any column exchange on the codewordsof the Rank1, Rank2, Rank3 and Rank4, and multiplying the codewords by aconstant coefficient, or performing row exchange on all codewords, areequivalent to the codebooks before the change.

The codebooks obtained by multiplying any column in the codewords ofRank1, Rank2, Rank3 and Rank4 by e^(jφ) are equivalent to the codebooksbefore the change, wherein φ is any non-zero real number.

The embodiments of the present invention further provide a terminal, asshown in FIG. 5, comprising:

a channel state information acquisition unit 501, configured to acquirechannel state information, the channel state information comprising afirst class of Precoding Matrix Indicator (PMI1) information and RankIndicator (RI) information;

an encoding unit 502, configured to perform joint encoding on the PMI1information and the RI information into a 4-bit or 5-bit feedbackreport, wherein the feedback report is used for indicating one of a setof combination information formed by the RI information and the PMI1information, and the set of combination information at least comprisesone of: combination information of RI=1 with M1 PMI1 respectively;

combination information of RI=2 with M2 PMI1 respectively;

combination information of RI=3 with one PMI1;

combination information of RI=4 with one PMI1;

wherein M1=M2=8, or M1=M2=4, or M1=16 and M2=8, or M1=8 and M2=16, orM1=16 and M2=4, or M1=4 and M2=16, or M1=8 and M2=4, or M1=4 and M2=8;and

a feedback unit 503, configured to feed back the feedback report in aphysical uplink control channel.

The embodiments of the present invention further provide a terminal, asshown in FIG. 6, comprising:

a channel state information acquisition unit 601, configured to acquirechannel state information, the channel state information comprising RankIndicator (RI) information, a second class of Precoding Matrix Indicator(PMI2) information, subband indication information and channel qualityinformation; and

a feedback unit 602, configured to feed back the channel stateinformation in a physical uplink control channel, wherein when RI=3 or4, the PMI2 information comprises 2 bits, and the PMI2 indicates onecodeword in a first set of codewords, and the first set of codewordscomprises 4 codewords selected from a codebook corresponding to Ranks 3and 4 in the Rel-8 codebook.

The embodiments of the present invention further provide a terminal, asshown in FIG. 7, comprising:

a channel state information acquisition unit 701, configured to acquirechannel state information, the channel state information comprising RankIndicator (RI) information, a second class of Precoding Matrix Indicator(PMI2) information, subband indication information, and channel qualityinformation; and

a feedback unit 702, configured to feed back the channel stateinformation in a physical uplink control channel, wherein when RI=1 or2, the PMI2 information comprises 2 bits, and indicates one codeword ina second set of codewords, and the second set of codewords comprises:

0^(th), 1^(st), 2^(nd), and 3rd codewords in a codebook corresponding torank 1 in the Long Term Evolution-Advanced (LTE-A) Rel12 version or afirst or second codebook corresponding to rank 2 in the LTE-A Rel12version; or

0^(th), 1^(st), 8^(th), and 9^(th) codewords in a codebook correspondingto rank 1 in the LTE-A Rel12 version or a first or second codebookcorresponding to rank 2 in the LTE-A Rel12 version; or

0^(th), 4^(th), 8^(th), and 12^(th) codewords in a codebookcorresponding to rank 1 in the LTE-A Rel12 version or a first or secondcodebook corresponding to rank 2 in the LTE-A Rel12 version; or

0^(th), 4^(th), 5^(th), and 12^(th) codewords in a codebookcorresponding to rank 1 in the LTE-A Rel12 version or a first or secondcodebook corresponding to rank 2 in the LTE-A Rel12 version; or

0^(th), 1^(st), 4^(th), and 5^(th) codewords in a codebook correspondingto rank 1 in the LTE-A Rel12 version or a first or second codebookcorresponding to rank 2 in the LTE-A Rel12 version; or

12^(th), 13^(th), 14^(th), and 15^(th) codewords in a codebookcorresponding to rank 1 in the LTE-A Rel12 version or a first or secondcodebook corresponding to rank 2 in the LTE-A Rel12 version.

The embodiments of the present invention further provide a terminal, asshown in FIG. 8, comprising:

a channel state information acquisition unit 801, configured to acquirechannel state information, the channel state information comprising RankIndicator (RI) information, a first class of Precoding Matrix Indicator(PMI1) information, and a second class of Precoding Matrix Indicator(PMI2) information;

an encoding unit 802, configured to perform joint encoding on the PMI1information and the PMI2 information into a 4-bit feedback report,wherein

the feedback report is used for indicating one of a set of combinationinformation formed by the PMI1 and the PMI2, and codewords indicated bythe set of combination information comprise codewords in a codebookcorresponding to Rank 1 or a first or second codebook corresponding toRank 2 in the Long Term Evolution-Advanced (LTE-A) Rel12 version; and

a feedback unit 803, configured to feed back the feedback report in aphysical uplink control channel.

It should be illustrated that many details described in the above methodembodiments may similarly be applied to the apparatus embodiments, andtherefore the repeated description of the same or similar parts areomitted.

A person having ordinary skill in the art should understand that all ora part of the steps in the above method can be implemented by programsinstructing related hardware, and the programs can be stored in acomputer readable storage medium, such as a read-only memory, a disk, ora disc etc. Alternatively, all or a part of the steps in theaforementioned embodiments can also be implemented with one or moreintegrated circuits. Accordingly, various modules/units in theaforementioned embodiments can be implemented in a form of hardware, orcan also be implemented in a form of software functional modules. Thepresent invention is not limited to any particular form of combinationof hardware and software.

The above description is merely preferable embodiments of the presentinvention, instead of limiting the protection scope of the presentinvention. Any modification, equivalent substitution, improvement etc.,which is made within the spirit and principle of the present invention,should be included in the protection scope of the present invention.

INDUSTRIAL APPLICABILITY

The embodiments of the present invention can reduce the overhead of thePMI feedback by joint encoding and can further ensure the accuracy ofthe PMI feedback with a limited overhead and obtain better precodingperformance.

What is claimed is:
 1. A method for feeding back channel stateinformation, applied to a 4-antenna system, comprising: a terminalacquiring channel state information, the channel state informationcomprising Rank Indicator (RI) information, a second class of PrecodingMatrix Indicator (PMI2) information, subband indication information andchannel quality information; and the terminal feeding back the channelstate information in a physical uplink control channel, wherein whenRI=3 or 4, the PMI2 information comprises 2 bits, and the PMI2 indicatesone codeword in a first set of codewords, and the first set of codewordscomprises 4 codewords selected from a codebook corresponding to Ranks 3and 4 in a Rel-8 codebook, wherein the Rel-8 codebook refers to thecodebook defined in 3GPP TS 36.211 V8.9.0; wherein the first set ofcodewords comprises: using 0^(th), 1^(st), 2^(nd), and 3^(rd) codewordsof the codebook corresponding to Ranks 3 and 4 in the Rel-8 codebook asa first group, using 8^(th), 9^(th), 10^(th), and 11^(th) codewords ofthe codebook corresponding to Ranks 3 and 4 in the Rel-8 codebook as asecond group, selecting 2 codewords from the first group and putting the2 codewords in the first set of codewords, and selecting 2 codewordsfrom the second group and putting the 2 codewords in the first set ofcodewords; or using 0^(th), 2^(nd), 8^(th), and 10^(th) codewords of thecodebook corresponding to Ranks 3 and 4 in the Rel-8 codebook as a thirdgroup, using 1^(st), 3^(rd), 9^(th), and 11^(th) codewords of thecodebook corresponding to Ranks 3 and 4 in the Rel-8 codebook as afourth group, selecting 2 codewords from the third group and putting the2 codewords in the first set of codewords, and selecting 2 codewordsfrom the fourth group and putting the 2 codewords in the first set ofcodewords; or using 0^(th), 2^(nd), 3^(rd), and 10^(th) codewords of thecodebook corresponding to Ranks 3 and 4 in the Rel-8 codebook as a fifthgroup, using 2^(nd), 8^(th), 9^(th), and 11^(th) codewords of thecodebook corresponding to Ranks 3 and 4 in the Rel-8 codebook as a sixthgroup, selecting 2 codewords from the fifth group and putting the 2codewords in the first set of codewords, and selecting 2 codewords fromthe sixth group and putting the 2 codewords in the first set ofcodewords; or using 0^(th), 1^(st), 2^(nd), and 9^(th) codewords of thecodebook corresponding to Ranks 3 and 4 in the Rel-8 codebook as aseventh group, using 3^(rd), 10^(th), 8^(th), and 11^(th) codewords ofthe codebook corresponding to Ranks 3 and 4 in the Rel-8 codebook as aneighth group, selecting 2 codewords from the seventh group and puttingthe 2 codewords in the first set of codewords, and selecting 2 codewordsfrom the eighth group and putting the 2 codewords in the first set ofcodewords.
 2. A method for feeding back channel state information,comprising: a terminal acquiring channel state information, the channelstate information comprising Rank Indicator (RI) information, a secondclass of Precoding Matrix Indicator (PMI2) information, subbandindication information and channel quality information; the terminalfeeding back the channel state information in a physical uplink controlchannel, wherein when RI=1 or 2, the PMI2 information is 2 bits, andindicates one codeword in a second set of codewords, and the second setof codewords consists of: 0^(th), 1^(st), 4^(th), and 5^(th) codewordsin a codebook corresponding to rank 1 in an LTE-A Rel12 version or0^(th), 1^(st), 4^(th), and 5^(th) codewords in a first or secondcodebook corresponding to rank 2 in the LTE-A Rel12 version, wherein theLTE-A Rel12 version refers to 3GPP TS 36.213 V12.0.0; wherein the methodis applied to a system having only 4 downlink antenna ports.
 3. A methodfor feeding back channel state information, applied to a 4-antennasystem, comprising: a terminal acquiring channel state information, thechannel state information comprising Rank Indicator (RI) information, afirst class of Precoding Matrix Indicator (PMI1) information and asecond class of Precoding Matrix Indicator (PMI2) information; theterminal performing joint encoding on the PMI1 information and the PMI2information into a 4-bit feedback report; the terminal feeding back thefeedback report in a physical uplink control channel; wherein thefeedback report is used for indicating one of a set of combinationinformation formed by the PMI1 and the PMI2, and codewords indicated bythe set of combination information comprise codewords in a codebookcorresponding to Rank 1 or a first or second codebook corresponding toRank 2 in a Long Term Evolution-Advanced (LTE-A) Rel12 version, whereinthe LTE-A Rel12 version refers to 3GPP TS 36.213 V12.0.0; wherein whenRI=1, the codewords indicated by the set of combination informationcomprise codewords in the codebook corresponding to Rank 1 in the LTE-ARel12 version, and the codewords indicated by the set of combinationinformation meet: a model ${{\begin{bmatrix}u \\{e^{j\frac{m\;\pi}{4}} \cdot e^{j\frac{n\;\pi}{2}} \cdot u}\end{bmatrix}\mspace{14mu} m} = 0},{{1\mspace{31mu} n} = 0},1,2,3,$wherein u is a 2-dimensional column vector; or when RI=2, the codewordsindicated by the set of combination information comprise codewords of afirst codebook corresponding to Rank 2 in the LTE-A Rel12 version, andthe codewords indicated by the set of combination information meet amodel ${\begin{bmatrix}u_{i_{1}} & u_{i_{2}} \\{e^{j\mspace{11mu}\theta_{m}}u_{i_{1}}} & {{- e^{j\;\theta_{m}}}u_{i_{2}}}\end{bmatrix}\mspace{14mu} i_{1}},i_{2},{m = {\left. 0 \right.\sim 15}},$wherein θ_(m) is any real number, and u_(i) is a 2-dimensional columnvector.
 4. The method according to claim 3, wherein all of the codewordsindicated by the set of combination information meet m=0; or one half ofthe codewords indicated by the set of combination information meet themodel when m=0, and the other half of the codewords indicated by the setof combination information meet the model when m=1; or all of thecodewords indicated by the set of combination information meet m=1. 5.The method according to claim 3, wherein a set of codewords indicated bythe set of combination information is: ${{\begin{bmatrix}u_{i} \\{e^{j\;\theta_{i}}u_{i}}\end{bmatrix}\mspace{14mu} i} = {\left. 0 \right.\sim 15}},$ whereinθ_(i) is any real number, and u_(i) is a 2-dimensional column vector. 6.A terminal, comprising: a channel state information acquisition unit,configured to acquire channel state information, the channel stateinformation comprising Rank Indicator (RI) information, a second classof Precoding Matrix Indicator (PMI2) information, subband indicationinformation and channel quality information; and a feedback unit,configured to feed back the channel state information in a physicaluplink control channel, wherein when RI=3 or 4, the PMI2 informationcomprises 2 bits, the PMI2 indicates one codeword in a first set ofcodewords, and the first set of codewords comprises 4 codewords selectedfrom a codebook corresponding to Ranks 3 and 4 in a Rel-8 codebook,wherein the Rel-8 codebook refers to the codebook defined in 3GPP TS36.211 V8.9.0; wherein the first set of codewords comprises: using0^(th), 1^(st), 2^(nd), and 3^(rd) codewords of the codebookcorresponding to Ranks 3 and 4 in the Rel-8 codebook as a first group,using 8^(th), 9^(th), 10^(th), and 11^(th) codewords of the codebookcorresponding to Ranks 3 and 4 in the Rel-8 codebook as a second group,selecting 2 codewords from the first group and putting the 2 codewordsin the first set of codewords, and selecting 2 codewords from the secondgroup and putting the 2 codewords in the first set of codewords; orusing 0^(th), 2^(nd), 8^(th), and 10^(th) codewords of the codebookcorresponding to Ranks 3 and 4 in the Rel-8 codebook as a third group,using 1^(st), 3^(rd), 9^(th), and 11^(th) codewords of the codebookcorresponding to Ranks 3 and 4 in the Rel-8 codebook as a fourth group,selecting 2 codewords from the third group and putting the 2 codewordsin the first set of codewords, and selecting 2 codewords from the fourthgroup and putting the 2 codewords in the first set of codewords; orusing 0^(th), 2^(nd), 3^(rd), and 10^(th) codewords of the codebookcorresponding to Ranks 3 and 4 in the Rel-8 codebook as a fifth group,using 2^(nd), 8^(th), 9^(th), and 11^(th) codewords of the codebookcorresponding to Ranks 3 and 4 in the Rel-8 codebook as a sixth group,selecting 2 codewords from the fifth group and putting the 2 codewordsin the first set of codewords, and selecting 2 codewords from the sixthgroup and putting the 2 codewords in the first set of codewords; orusing 0^(th), 1^(st), 2^(nd), and 9^(th) codewords of the codebookcorresponding to Ranks 3 and 4 in the Rel-8 codebook as a seventh group,using 3^(rd), 10^(th), 8^(th), and 11^(th) codewords of the codebookcorresponding to Ranks 3 and 4 in the Rel-8 codebook as an eighth group,selecting 2 codewords from the seventh group and putting the 2 codewordsin the first set of codewords, and selecting 2 codewords from the eighthgroup and putting the 2 codewords in the first set of codewords.
 7. Aterminal, comprising: a channel state information acquisition unit,configured to acquire channel state information, the channel stateinformation comprising Rank Indicator (RI) information, a second classof Precoding Matrix Indicator (PMI2) information, subband indicationinformation and channel quality information; and a feedback unit,configured to feed back the channel state information in a physicaluplink control channel, wherein, when RI=1 or 2, the PMI2 information is2 bits, and indicates one codeword in a second set of codewords, and thesecond set of codewords consists of: 0^(th), 1^(st), 4^(th), and 5^(th)codewords in a codebook corresponding to rank 1 in an LTE-A Rel12version or 0^(th), 1^(st), 4^(th), and 5^(th) codewords in a first orsecond codebook corresponding to rank 2 in the LTE-A Rel12 version,wherein the LTE-A Rel12 version refers to 3GPP TS 36.213 V12.0.0;wherein the terminal feeds back the channel state information to asystem having only 4 downlink antenna ports.
 8. A terminal, comprising:a channel state information acquisition unit, configured to acquirechannel state information, the channel state information comprising RankIndicator (RI) information, a first class of Precoding Matrix Indicator(PMI1) information and a second class of Precoding Matrix Indicator(PMI2) information; an encoding unit, configured to perform jointencoding on the PMI1 information and the PMI2 information into a 4-bitfeedback report, wherein the feedback report is used for indicating oneof a set of combination information formed by the PMI1 and the PMI2, andcodewords indicated by the set of combination information comprisecodewords in a codebook corresponding to Rank 1 or a first or secondcodebook corresponding to Rank 2 in a Long Term Evolution-Advanced(LTE-A) Rel12 version, wherein the LTE-A Rel12 version refers to 3GPP TS36.213 V12.0.0; and a feedback unit, configured to feed back thefeedback report in a physical uplink control channel; wherein when theRI=1, the codewords indicated by the set of combination informationcomprise codewords in the codebook corresponding to Rank 1 in the LTE-ARel12 version, and the codewords indicated by the set of combinationinformation meet: a model ${\begin{bmatrix}u \\{e^{j\frac{m\;\pi}{4}} \cdot e^{j\frac{n\;\pi}{2}} \cdot u}\end{bmatrix}\mspace{14mu} m} = {{0,1\mspace{14mu} n} = {0,1,2,3,}}$wherein u is a 2-dimensional column vector; or wherein when RI=2,codewords indicated by the set of combination information comprisecodewords of a first codebook corresponding to Rank 2 in the LTE-A Rel12version, and the codewords indicated by the set of combinationinformation meet a model ${\begin{bmatrix}u_{i_{1}} & u_{i_{2}} \\{e^{j\;\theta_{m}}u_{i_{1}}} & {{- e^{j\;\theta_{m}}}u_{i_{2}}}\end{bmatrix}\mspace{14mu} i_{1}},i_{2},{m = {\left. 0 \right.\sim 15}},$wherein θ_(m) is any real number, and u_(i) is a 2-dimensional columnvector.
 9. The terminal according to claim 8, wherein all of thecodewords indicated by the set of combination information meet m=0; orone half of the codewords indicated by the set of combinationinformation meet the model when m=0, and the other half of the codewordsindicated by the set of combination information meet the model when m=1;or all of the codewords indicated by the set of combination informationmeet m=1.
 10. The terminal according to claim 8, wherein a set ofcodewords indicated by the set of combination information is:${{\begin{bmatrix}u_{i} \\{e^{j\;\theta_{i}}u_{i}}\end{bmatrix}\mspace{14mu} i} = {\left. 0 \right.\sim 15}},$ whereinθ_(i) is any real number, and u_(i) is a 2-dimensional column vector.11. The method according to claim 5, wherein the${u_{i} \in \left\{ {{{{{{{\begin{bmatrix}1 \\1\end{bmatrix}\begin{bmatrix}1 \\e^{j\frac{\pi}{4}}\end{bmatrix}}\begin{bmatrix}1 \\j\end{bmatrix}}\begin{bmatrix}1 \\e^{j\frac{3\pi}{4}}\end{bmatrix}}\begin{bmatrix}1 \\{- 1}\end{bmatrix}}\begin{bmatrix}1 \\e^{j\frac{5\pi}{4}}\end{bmatrix}}\begin{bmatrix}1 \\{- j}\end{bmatrix}}\begin{bmatrix}1 \\e^{j\frac{7\pi}{4}}\end{bmatrix}} \right\}},$ wherein in {u_(i), i=0˜15}, 2 values are$\begin{bmatrix}1 \\1\end{bmatrix},$ 2 values are $\begin{bmatrix}1 \\e^{j\frac{\pi}{4}}\end{bmatrix},$ 2 values are $\begin{bmatrix}1 \\j\end{bmatrix},$ 2 values are $\begin{bmatrix}1 \\e^{j\frac{3\pi}{4}}\end{bmatrix},$ 2 values are $\begin{bmatrix}1 \\{- 1}\end{bmatrix},$ 2 values are $\quad{\begin{bmatrix}1 \\e^{j\frac{5\pi}{4}}\end{bmatrix},}$ 2 values are $\begin{bmatrix}1 \\{- j}\end{bmatrix},$ and 2 values are $\begin{bmatrix}1 \\e^{j\frac{7\pi}{4}}\end{bmatrix}.$
 12. The method according to claim 3, wherein for all thei₁ and i₂, i₁=i₂; or in the codewords, one half of the codewords meeti₂=i₁, and the other half of the codewords meet i₂≠i₁; or$u_{i_{1}},{u_{i_{2}} \in \left\{ {{{{{{{\begin{bmatrix}1 \\1\end{bmatrix}\begin{bmatrix}1 \\e^{j\frac{\pi}{4}}\end{bmatrix}}\begin{bmatrix}1 \\j\end{bmatrix}}\begin{bmatrix}1 \\e^{j\frac{3\pi}{4}}\end{bmatrix}}\begin{bmatrix}1 \\{- 1}\end{bmatrix}}\begin{bmatrix}1 \\e^{j\frac{5\pi}{4}}\end{bmatrix}}\begin{bmatrix}1 \\{- j}\end{bmatrix}}\begin{bmatrix}1 \\e^{j\frac{7\pi}{4}}\end{bmatrix}} \right\}},$ wherein in {u_(i) ₁ ,u_(i) ₂ , i=0˜15}, 2values of u_(i) ₁ ,u_(i) ₂ are $\quad{\begin{bmatrix}1 \\1\end{bmatrix},}$ 2 values of u_(i) ₁ ,u_(i) ₂ are $\begin{bmatrix}1 \\e^{j\frac{\pi}{4}}\end{bmatrix},$ 2 values of u_(i) ₁ ,u_(i) ₂ are $\begin{bmatrix}1 \\j\end{bmatrix},$ 2 values of u_(i) ₁ ,u_(i) ₂ are $\begin{bmatrix}1 \\e^{j\frac{3\pi}{4}}\end{bmatrix},$ 2 values of u_(i) ₁ ,u_(i) ₂ are $\begin{bmatrix}1 \\{- 1}\end{bmatrix},$ 2 values of u_(i) ₁ ,u_(i) ₂ are $\begin{bmatrix}1 \\e^{j\frac{5\pi}{4}}\end{bmatrix},$ 2 values of u_(i) ₁ ,u_(i) ₂ are $\begin{bmatrix}1 \\{- j}\end{bmatrix},$ and 2 values of u_(i) ₁ ,u_(i) ₂ are$\quad\begin{bmatrix}1 \\e^{j\frac{7\pi}{4}}\end{bmatrix}$ respectively; or when RI=2, codewords indicated by theset of combination information comprise codewords of a second codebookcorresponding to Rank 2 in the LTE-A Rel12 version, and the codewordsindicated by the set of combination information meet a model${\begin{bmatrix}u_{i_{1}} & u_{i_{3}} \\{e^{j\;\theta_{m}}u_{i_{2}}} & {e^{j\;\theta_{n}}u_{i_{4}}}\end{bmatrix}\mspace{14mu} i_{1}},i_{2},i_{3},i_{4},m,{n = {\left. 0 \right.\sim 15}},$wherein θ_(m),θ_(n) are any real numbers, and u_(i) is a 2-dimensionalcolumn vector, wherein the u_(i) ₁ ,u_(i) ₂ ,u_(i) ₃ ,u_(i) ₄ meeti₂=i₁=i₄=i₃.
 13. The terminal according to claim 10, wherein${u_{i} \in \left\{ {{{{{{{\begin{bmatrix}1 \\1\end{bmatrix}\begin{bmatrix}1 \\e^{j\frac{\pi}{4}}\end{bmatrix}}\begin{bmatrix}1 \\j\end{bmatrix}}\begin{bmatrix}1 \\e^{j\frac{3\pi}{4}}\end{bmatrix}}\begin{bmatrix}1 \\{- 1}\end{bmatrix}}\begin{bmatrix}1 \\e^{j\frac{5\pi}{4}}\end{bmatrix}}\begin{bmatrix}1 \\{- j}\end{bmatrix}}\begin{bmatrix}1 \\e^{j\frac{7\pi}{4}}\end{bmatrix}} \right\}},$ wherein in {u_(i), i=0˜15}, 2 values are$\begin{bmatrix}1 \\1\end{bmatrix},$ 2 values are $\begin{bmatrix}1 \\e^{j\frac{\pi}{4}}\end{bmatrix},$ 2 values are $\begin{bmatrix}1 \\j\end{bmatrix},$ 2 values are $\begin{bmatrix}1 \\e^{j\frac{3\pi}{4}}\end{bmatrix},$ 2 values are $\begin{bmatrix}1 \\{- 1}\end{bmatrix},$ 2 values are $\begin{bmatrix}1 \\e^{j\frac{5\pi}{4}}\end{bmatrix},$ 2 values are $\begin{bmatrix}1 \\{- j}\end{bmatrix},$ and 2 values are $\begin{bmatrix}1 \\e^{j\frac{7\;\pi}{4}}\end{bmatrix}.$
 14. The terminal according to claim 8, wherein for allthe i₁ and i₂, i₁=i₂ or in the codewords, one half of the codewords meeti₂=i₁, and the other half of the codewords meet i₂≠i₁; or the$u_{i_{1}},{u_{i_{2}} \in \left\{ {{{{{{{\begin{bmatrix}1 \\1\end{bmatrix}\begin{bmatrix}1 \\e^{j\frac{\pi}{4}}\end{bmatrix}}\begin{bmatrix}1 \\j\end{bmatrix}}\begin{bmatrix}1 \\e^{j\frac{3\pi}{4}}\end{bmatrix}}\begin{bmatrix}1 \\{- 1}\end{bmatrix}}\begin{bmatrix}1 \\e^{j\frac{5\pi}{4}}\end{bmatrix}}\begin{bmatrix}1 \\{- j}\end{bmatrix}}\begin{bmatrix}1 \\e^{j\frac{7\pi}{4}}\end{bmatrix}} \right\}},$ wherein in {u_(i) ₁ ,u_(i) ₂ , i=0˜15}, 2values of u_(i) ₁ ,u_(i) ₂ are $\begin{bmatrix}1 \\1\end{bmatrix},$ 2 values of u_(i) ₁ ,u_(i) ₂ are $\begin{bmatrix}1 \\e^{j\frac{\pi}{4}}\end{bmatrix},$ 2 values of u_(i) ₁ ,u_(i) ₂ are $\begin{bmatrix}1 \\j\end{bmatrix},$ 2 values of u_(i) ₁ ,u_(i) ₂ are $\begin{bmatrix}1 \\e^{j\frac{3\pi}{4}}\end{bmatrix},$ 2 values of u_(i) ₁ ,u_(i) ₂ are $\begin{bmatrix}1 \\{- 1}\end{bmatrix},$ 2 values of u_(i) ₁ ,u_(i) ₂ are $\begin{bmatrix}1 \\e^{j\frac{5\pi}{4}}\end{bmatrix},$ 2 values of u_(i) ₁ ,u_(i) ₂ are $\begin{bmatrix}1 \\{- j}\end{bmatrix},$ and 2 values of u_(i) ₁ ,u_(i) ₂ are $\begin{bmatrix}1 \\{\mathbb{e}}^{j\frac{7\pi}{4}}\end{bmatrix}_{\;}$ respectively; or when the RI=2, codewords indicatedby the set of combination information comprise codewords of a secondcodebook corresponding to Rank 2 in the LTE-A Rel12 version, and thecodewords indicated by the set of combination information meet a model$\begin{bmatrix}u_{i_{1}} & u_{i_{3}} \\{{\mathbb{e}}^{j\;\theta_{m}}u_{i_{2}}} & {{\mathbb{e}}^{{j\theta}_{n}}u_{i_{4}}}\end{bmatrix}$ i₁, i₂, i₃, i₄, m, n = 0 ∼ 15, wherein θ_(m),θ_(n) areany real numbers, and u_(i) is a 2-dimensional column vector, whereinthe u_(i) ₁ ,u_(i) ₂ ,u_(i) ₃ ,u_(i) ₄ meet i₂=i₁=i₄=i₃.